Constitutive Variation in Hepatic Expression of Porcine Innate

Constitutive Variation in Hepatic Expression of Porcine Innate Immune Genes Associated with

Novel Promoter Polymorphisms

By

Heindrich Nicolaas Snyman

A Thesis

Presented to

The Faculty of Graduate Studies

of

The University of Guelph

In partial fulfilment of the requirements

for the degree of

Doctor of Veterinary Science

Guelph, Ontario, Canada

© Heindrich Nicolaas Snyman, November, 2013

ABSTRACT

CONSTITUTIVE VARIATION IN HEPATIC EXPRESSION OF PORCINE INNATE

IMMUNE GENES ASSOCIATED WITH NOVEL PROMOTER POLYMORPHISMS

Heindrich N. Snyman Advisor

University of Guelph, 2013 Dr. Brandon Lillie

Infectious diseases are an important factor limiting production, growth performance,

economics and animal welfare in the global swine industry. Numerous pathogenic, environmental and

host genetic factors contribute to infectious disease susceptibility, including defects in the innate

immune system. The secreted, membrane-bound and intracellular proteins of the innate immune

system are critical components in the defense against infectious pathogens, especially in young pigs.

Previous studies have identified a number of single nucleotide polymorphisms (SNPs) in the innate

immune genes of pigs, some of which are more frequent in pigs with economically important

infectious diseases such as enteritis, serositis and pneumonia. Additional novel genetic differences

(SNPs, insertions, deletions or other genetic variations) that alter the expression and/or function of

important resistance-conferring innate immune proteins could, together with previously identified

markers, form the basis for future development of genetic selection strategies aimed at increasing

innate disease resistance in pigs. In this thesis, genome-wide expression analysis and DNA

sequencing were used to screen for polymorphisms that were associated with decreased or increased

expression of selected innate immune genes in the liver of healthy market weight pigs. Using

expression microarrays, innate immune genes were identified that exhibited widely variable hepatic

gene expression. The promoter regions of these variably expressed genes were characterized and

novel promoter SNPs, insertions and deletions were identified in genes coding for proteins such as

secretoglobin, family 1A, member 1; porcine surfactant protein D; retinoic acid-inducible gene 1 and

porcine hepcidin antimicrobial peptide. Some of these SNPs were found to be more prevalent in

animals with either impaired or enhanced hepatic gene expression. Genotyping healthy and diseased

pigs using MassArray MALDI-TOF mass spectrometry revealed that genetic defects were widely

variable in their frequency in different breeds of pigs and some were more or less frequent in pigs

with certain common infectious diseases and/or pathogens. Information from these studies will be

used to develop a comprehensive panel of genetic markers that can be used to breed for pigs with

increased disease resistance. Such a panel could help improve pig production, promote animal health

and welfare, and decrease the need for antimicrobial drugs.

iv

ACKNOWLEDGEMENTS

I would like to extend my most sincere gratitude to my advisor and mentor, Dr. Brandon Lillie, whose

support, guidance and continued encouragement was an integral component to the success of my

research project and graduate training as a veterinary pathologist.

I am also extremely grateful to the pathologists within the Department of Pathobiology for their

mentorship and training throughout my journey towards becoming a successful veterinary pathologist

and to my thesis advisory committee, Dr. Jeff Caswell, Dr.Tony Hayes and Dr. Jim Squires for their

invaluable insights, advice and support throughout my DVSc studies.

I would also like to sincerely thank Dr. Jutta Hammermueller for sharing her knowledge and

experimental expertise and to Dr. Jim Squires (Department of Animal & Poultry Science), Dr. Alex

Martinez (CFIA), Dr. Balu Odedra (CFIA) and the pathologists at the Animal Health Laboratory,

University of Guelph for assistance in obtaining liver samples. I am very appreciative of the

assistance provided by research assistants and summer research students involved in this project;

especially Kelsie Jagt, Sarah Mavin, Eric Nham and David Balogh.

I am also extremely grateful to Dr. Edana Cassol for sharing her expertise and guidance in generating

microarray expression heat maps and Dr. Sharon Cassol for always being available to assist me in

whichever way possible.

I express my gratitude to all funding agencies (Ontario Veterinary College; NSERC; OMAFRA,

Ontario Pork and the Canadian Centre for Swine Improvement) for their financial assistance. Without

their support this research would not have been possible.

To my parents and family: “Ek wil ook baie graag my ouers en familie bedank vir hul

onvoorwaardelike liefde en ondersteuning vir alles wat ek aanpak in my lewe”.

Finally, I am eternally grateful for the endless love and support of my wife, Roberta, and children,

Zander and Myra, whom have made my Canadian journey especially rewarding.

v

DECLARATION OF WORK PERFORMED

With few exceptions (as listed below), all of the work in this thesis was performed by Heindrich

Nicolaas Snyman under the supervision of Dr. Brandon Lillie and an advisory committee composed

of Dr. Jeff Caswell, Dr. Tony Hayes and Dr. Jim Squires.

Dr. Brandon Lillie assisted with the collection of liver samples.

Dr. Jutta Hammermueller (Department of Pathobiology, University of Guelph) assisted with some of

the nucleic acid extractions and real-time PCR assays.

Kelsie Jagt, a summer research student (Department of Molecular and Cellular Biology, University of

Guelph) under my supervision performed some of the real-time PCR, promoter region sequencing and

restriction fragment length polymorphism analyses for surfactant protein D.

David Balogh, an in-course master’s degree student (Department of Biomedical Science, University

of Guelph) under my supervision performed some of the initial primer design and promoter

amplification for peptidoglycan recognition proteins 1 and 2.

vi

TABLE OF CONTENTS

ACKNOWLEDGEMENTS ................................................................................................................... iv

DECLARATION OF WORK PERFORMED ........................................................................................ v

LIST OF TABLES ............................................................................................................................... viii

LIST OF FIGURES ............................................................................................................................... xi

LIST OF ABBREVIATIONS .............................................................................................................. xiii

GENERAL INTRODUCTION, HYPOTHESES AND OBJECTIVES ................................................. 1

GENERAL INTRODUCTION .......................................................................................................... 1

HYPOTHESES ................................................................................................................................... 3

OBJECTIVES ..................................................................................................................................... 3

CHAPTER 1: STRUCTURE, FUNCTION AND GENETICS OF PORCINE INNATE IMMUNE PROTEINS…… ..................................................................................................................................... 4

INTRODUCTION .............................................................................................................................. 4

TOLL-LIKE RECEPTORS ................................................................................................................ 6

COLLECTINS AND FICOLINS (COLLAGENOUS LECTINS) ................................................... 13

C-TYPE LECTIN RECEPTORS AND SCAVENGER RECEPTORS ........................................... 21

GALECTINS .................................................................................................................................... 22

RETINOIC ACID-INDUCIBLE GENE-1-LIKE RECEPTORS ..................................................... 26

NUCLEOTIDE OLIGOMERIZATION DOMAIN-LIKE RECEPTORS ....................................... 30

ANTIMICROBIAL PEPTIDES ....................................................................................................... 34

PEPTIDOGLYCAN RECOGNITION PROTEINS ......................................................................... 38

COMPLEMENT ............................................................................................................................... 42

GENETIC POLYMORPHISM AND THE INNATE IMMUNE GENOME ................................... 46

CHAPTER 2: CONSTITUTIVE VARIATION IN THE HEPATIC INNATE IMMUNE TRANSCRIPTOME OF HEALTHY PIGS .......................................................................................... 53

ABSTRACT ..................................................................................................................................... 53

INTRODUCTION ............................................................................................................................ 54

MATERIALS AND METHODS ..................................................................................................... 56

RESULTS ......................................................................................................................................... 62

DISCUSSION ................................................................................................................................... 82

CHAPTER 3: NOVEL PROMOTER POLYMORPHISMS ASSOCIATED WITH INCREASED CONSTITUTIVE EXPRESSION OF SCGB1A1 AND SFTPD mRNA IN THE LIVER OF HEALTHY PIGS .................................................................................................................................. 89

ABSTRACT ..................................................................................................................................... 89

INTRODUCTION ............................................................................................................................ 91

MATERIALS AND METHODS ..................................................................................................... 93

RESULTS ....................................................................................................................................... 103

DISCUSSION ................................................................................................................................. 117

CHAPTER 4: VARIATION IN CONSTITUTIVE HEPATIC GENE EXPRESSION OF HAMP AND DDX58 WITH IDENTIFICATION OF NOVEL PROMOTER POLYMORPHISMS ............ 123

vii

ABSTRACT ................................................................................................................................... 123

INTRODUCTION .......................................................................................................................... 124

MATERIALS AND METHODS ................................................................................................... 126

RESULTS ....................................................................................................................................... 132

DISCUSSION ................................................................................................................................. 160

GENERAL DISCUSSION ................................................................................................................. 167

SUMMARY AND CONCLUSIONS ................................................................................................. 174

REFERENCES. .................................................................................................................................. 177

APPENDIX I: LIST OF PREVIOUSLY IDENTIFIED INNATE IMMUNE GENE SNPS USED FOR MALDI-TOF MASS SPECTROMETRY SNP GENOTYPING .............................................. 206

APPENDIX II: RANKING OF INNATE IMMUNE GENES BY VARIATION IN CONSTITUTIVE GENE EXPRESSION (TOP 6 % VS. BOTTOM 50 %) ...................................... 207

APPENDIX III: COMPARISON OF RANKING OF ALL INNATE IMMUNE RESPONSE GENE PROBES .................................................................................................................................. 212

APPENDIX IV. TARGET INNATE IMMUNE RESPONSE GENE SEQUENCES WITH ANNOTATED SNPS ......................................................................................................................... 222

viii

LIST OF TABLES

Table 1.1. Ligand and cellular localization of the Toll-like receptors. ................................................. 48

Table 1.2. Sugar specificity and species distribution of various collagenous lectins. .......................... 49

Table 1.3. Ligand and cellular localization of the C-type lectin receptors and scavenger receptors. ... 50

Table 1.4. Ligand and cellular localization of the retinoic acid-inducible gene-I–like receptors. ........ 51

Table 1.5. Ligand and cellular localization of the peptidoglycan recognition proteins. ....................... 52

Table 2.1. List of previously identified innate immune response gene SNPs used for microarray

expression selection. ............................................................................................................................. 60

Table 2.2. Primers used for PCR based sex-genotyping. ...................................................................... 60

Table 2.3. Selected microarray reference genes and calculated gene expression ratio. ........................ 61

Table 2.4. Selected microarray acute phase protein genes and calculated gene expression ratios. ...... 67

Table 2.5. Ranking of innate immune genes by variation in constitutive gene expression. ................. 68

Table 2.6. List of innate immune genes with multiple microarray probes with poor internal probe

correlation. ............................................................................................................................................ 73

Table 2.7. Constitutive variation in innate immune gene expression is not correlated with acute

phase protein expression. ...................................................................................................................... 74

Table 3.1. Primers used for promoter region amplification, sequencing and RFLP assays of

SCGB1A1 and SFTPD. ....................................................................................................................... 100

Table 3.2. Restriction endonucleases used in RFLP assays to genotype pigs for SFTPD promoter

polymorphisms. ................................................................................................................................... 101

Table 3.3. Primers used for semi-quantitative real-time RT-PCR for SCBG1A1 and SFTPD. .......... 102

Table 3.4. Identified SCGB1A1 sequence variations. ......................................................................... 106

Table 3.5. Effect of the SFTPD g.-4509A>G SNP on hepatic gene expression. ................................ 113

Table 3.6. Frequency of variant positive genotypes for the SFTPD g.-4509A>G SNP in pigs

diagnosed with different disease syndromes, bacterial and viral pathogens. ...................................... 114

Table 3.7. Frequency of variant positive genotypes for the SFTPD g.-4509A>G promoter SNP in

purebred pigs. ...................................................................................................................................... 115

ix

Table 3.8. p-values for pair-wise comparisons of SFTPD g.-4509A>G SNP variant genotype

frequencies in purebred pigs. .............................................................................................................. 115

Table 3.9. Frequency of variant positive genotypes for the SFTPD g.-4509A>G promoter SNP in

weighted cross bred pig populations. .................................................................................................. 115

Table 4.1. Primers used for promoter region amplification and sequencing of DDX58, HAMP,

PGLYRP1 and PGLYRP. .................................................................................................................... 130

Table 4.2. Primers used for semi-quantitative real-time RT-PCR assays of DDX58 and HAMP. ...... 131

Table 4.3. Identified HAMP sequence variations. ............................................................................... 139

Table 4.4. Relative allele frequencies of HAMP promoter variants between high and low

expressing groups. ............................................................................................................................... 140

Table 4.5. Identified DDX58 sequence variations. ............................................................................. 141

Table 4.6. Relative allele frequencies of DDX58 promoter variants between high and low

expressing groups. ............................................................................................................................... 142

Table 4.7. Mean hepatic gene expression of HAMP and DDX58 in variant genotypes. ..................... 143

Table 4.8. Effect of variant genotype on HAMP and DDX58 expression. .......................................... 144

Table 4.9. Co-expressing haplotypes identified for HAMP and DDX58 promoter polymorphisms. .. 146

Table 4.10. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169

polymorphisms in diseased groups. .................................................................................................... 147

Table 4.11. Calculated p- and q-values for HAMP, DDX58, CD163 and CD169 polymorphisms in

diseased groups. .................................................................................................................................. 148


polymorphisms in pigs diagnosed with different bacterial pathogens. ............................................... 149


pigs diagnosed with different bacterial pathogens. ............................................................................. 150


polymorphisms in pigs diagnosed with different viral pathogens. ..................................................... 151


pigs diagnosed with different viral pathogens. ................................................................................... 152

x


polymorphisms in purebred pigs. ........................................................................................................ 153

Table 4.17. p-values for pair-wise comparisons of HAMP, DDX58, CD163 and CD169

polymorphism variant genotype frequencies in purebred pigs. .......................................................... 154


polymorphisms in weighted cross bred pig populations. .................................................................... 156

xi

LIST OF FIGURES

Figure 2.1. Unsupervised agglomerative hierarchical clustering of innate immune gene expression. . 75

Figure 2.2. Microarray expression of representative examples of the four distinct expression

pattern/clusters. ..................................................................................................................................... 77

Figure 2.3. Melting curve analysis of the TSPY and MT-CYB duplex sex-genotyping assay. .............. 78

Figure 2.4. Normalized microarray expression of DDX3Y. ................................................................. 79

Figure 2.5. Hepatic expression of MBL2 in MBL2 g.-1091G>A SNP genotypes measured by

microarray and semi-quantitative real-time RT-PCR. .......................................................................... 80

Figure 2.6. Microarray expression of MBL2. ........................................................................................ 81

Figure 3.1. SCGB1A1 promoter amplification of top and bottom eight expressing pigs. ................... 108

Figure 3.2. Regional Ensembl annotation of Sus scrofa chromosome number 2. .............................. 109

Figure 3.3. Correlation between SCGB1A1 mRNA expression as measured by semi-quantitative

real-time RT-PCR and microarray. ..................................................................................................... 110

Figure 3.4. Restriction length fragment polymorphism analyses developed to genotype pigs for the

three identified SFTPD promoter SNPs. ............................................................................................. 111

Figure 3.5. Microarray expression of SFTPD. .................................................................................... 112

Figure 3.6. Hepatic expression of SFTPD in SFTPD g.-4509A>G SNP genotypes. .......................... 113

Figure 3.7. Frequency of variant positive genotypes for the SFTPD g.-4509A>G SNP in healthy

pure bred and cross bred pigs. ............................................................................................................. 116

Figure 4.1. Hepatic expression of HAMP and DDX58 with respect to polymorphism genotypes. .... 145

Figure 4.2. Correlation of semi-quantitative real-time RT-PCR and microarray mRNA expression

of DDX58. ........................................................................................................................................... 157

Figure 4.3. Correlation of DDX58 mRNA expression levels when measured using two different

microarray probes. .............................................................................................................................. 158

Figure 4.4. Correlation of HAMP mRNA expression levels when measured using two different

microarray probes. .............................................................................................................................. 159

Figure IV.1. Sus scrofa SCGB1A1 amplified promoter sequence. ..................................................... 222

xii

Figure IV.2. Sus scrofa SFTPD amplified promoter sequence. .......................................................... 223

Figure IV.3. Sus scrofa HAMP amplified promoter sequence. ........................................................... 224

Figure IV.4. Sus scrofa DDX58 amplified promoter sequence. .......................................................... 225

Figure IV.5. Sus scrofa PGLYRP1 amplified promoter sequence. ..................................................... 226

Figure IV.6. Sus scrofa PGLYRP2 amplified promoter sequence. ..................................................... 227

xiii

LIST OF ABBREVIATIONS

28S

APP

B2M

bp

C1q

C1r

C1s

C2

C3

C4

cDNA

CRD

CRP

DAMP

DEPC

FBG

FC

FDR

GalNAc

GAPDH

GER

Glc

GlcNAc

HAMP

HP

LacNAc

LPS

LW

MALDI-TOF

28s ribosomal RNA

Actinobacillus pleuropneumoniae

beta-2 microglobulin

base pairs

complement component C1q

C1q-associated serine protease C1r

C1q-associated serine protease C1s

complement component C2



cDNA - complementary DNA

carbohydrate-recognition domain

C-reactive protein

danger-associated molecular pattern

ditheythylenepyrocarbonate

fibrinogen-like domain

fold change

false discovery rate

N-acetylgalactosamine

glyceraldehyde-3-phosphate dehydrogenase

gene expression ratio

glucose

N-acetyl-D-glucosamine

hepcidin antibacterial peptide

haptoglobin

N-acetyllactosamine

lipopolysaccharide

large white

matrix-assisted laser desorption/ionization time of flight

xiv

MASP

MBL

mRNA

NCBI

PAMP

PCR

PCV2

PGLYRP-1

PGLYRP-2

PGLYRPs

FCN

pig-MAP

PRR

PRRSV

RFLP

RIG-1

RT-PCR

SAA

SCGB1A1

SNP

SP-A

SP-D

TLR

Tris

UTR

MBL-associated serine protease

mannan-binding lectin (mannose-binding lectin)

messenger RNA

National Center for Biotechnology Information

pathogen-associated molecular pattern

polymerase-chain reaction

porcine circovirus type 2

peptidoglycan recognition protein-1

peptidoglycan recognition protein-2

mammalian peptidoglycan recognition proteins

ficolin

pig major acute phase protein/ inter-α-trypsin inhibitor

pattern recognition receptor

porcine reproductive and respiratory syndrome virus

restriction fragment length polymorphism

retinoic acid-inducible gene 1

reverse-transcriptase polymerase chain reaction

serum amyloid A

secretoglobin, family 1A, member 1 (uteroglobin)

single nucleotide polymorphism

surfactant protein A

surfactant protein D

Toll-like receptor

tris(hydroxymethyl)aminomethane

untranslated region

1

GENERAL INTRODUCTION, HYPOTHESES AND OBJECTIVES

GENERAL INTRODUCTION

Significant progress has been made in the control of infectious diseases through ongoing

advances in biosecurity, disease management and vaccination. Despite this progress, infectious

diseases are still one of the most important factors limiting production, growth performance,

economics and animal welfare in the global swine industry. Pathogen, environmental, and host

genetic factors contribute to this multifactorial problem. The problem is further confounded by the

fact that common infectious disease syndromes in pigs are often caused by multiple co-infecting

bacterial and viral pathogens. Regardless of the management strategy of different production units, the

identification of pigs that are better able to respond to infectious stimuli can provide insights for

enhancing disease resistance. General health and resistance phenotypes have been shown to be

heritable traits, regardless of the prevailing environmental conditions and the selection of pigs based

on disease resistance phenotypes has been shown to improve production characteristics (Clapperton et

al. 2009, Mellencamp et al. 2008, Wilkie and Mallard 1999). The use of quantitative trait loci (QTL)

allows for the identification and selection of desirable traits (Rothschild 2004, Rothschild et al. 2007).

QTL and disease resistance phenotypes are often polygenic receiving variable contributions from a

large number of genes and many of the underlying variations in these loci have not been extensively

investigated. As a result there is an opportunity to characterize disease resistance phenotypes at a

complex genetic level. Few studies have focussed on genetic defects in the innate immune system of

swine and other domestic animals, or on the potential of these defects to alter disease susceptibility

and/or severity. However a growing body of evidence suggests that genetic polymorphisms in innate

response genes of pigs and other domestic animals can have a detrimental effect on the incidence of

common disease syndromes and susceptibility of these animals to common infectious pathogens

(Jozaki et al. 2009, Juul-Madsen et al. 2011, Keirstead et al. 2011, Lillie et al. 2007, Uenishi et al.

2011, Uenishi et al. 2012, Wang et al. 2011). Identification of novel genetic differences (SNPs,

insertions, deletions or other genetic variations) that alter the expression and/or function of important

resistance-conferring proteins could, together with previously identified markers, form the basis of

2

genetic selection strategies aimed at increasing innate disease resistance in pigs. To date, most studies

of genetic variation have used a targeted single gene approach. These studies have successfully

identified a small number of candidate SNPs that are associated with altered gene expression. As a

result of the focussed nature of these studies, many innate immune genes have not been investigated

and considering the redundancy and complexity of the innate immune system, an opportunity exists to

further expand these studies. Recent advances in sequencing and annotation of the porcine genome,

combined with porcine specific whole genome microarray expression technology, now provides the

opportunity to expand these efforts into a genome-wide approach. In this study, we investigated

whether microarray technology could be used to identify innate immune genes that exhibited

markedly variable gene expression in healthy pigs. The study was based on the premise that, by

detecting target genes that exhibited wide variation in constitutive gene expression and determining

the underlying reasons for this altered gene expression, we would be able to identify genetic

differences that had a major impact on the expression of innate immune response proteins. We also

reasoned that these mutations (SNPs, insertions, deletions) would provide a valuable set of markers

for the development of a comprehensive genetic selection panel that could be used to increase disease

resistance in the commercial swine population. The ability to select for higher innate disease

resistance would result in increased production, promote animal health and welfare and decrease the

need for antimicrobial drugs in commercial pig populations.

3

HYPOTHESES

1. Altered hepatic expression of innate immune proteins can impair disease resistance to some

common infectious diseases

2. In some pigs, this altered expression, may be due to specific genetic variations such as

insertions, deletions and single nucleotide polymorphisms

3. Knowledge of genetic variations associated with impaired disease resistance could be used to

improve the health and production capacities of these animals

OBJECTIVES

1. Identify innate immune genes with widely variable expression in healthy pigs

2. Identify and characterize polymorphisms and other genetic variations in the promoter region

of these genes

3. Determine the impact of identified genetic variants on gene expression

4. Determine the frequency of these genetic variants in pigs with commonly encountered

infectious diseases and pathogens of swine

4

CHAPTER 1: STRUCTURE, FUNCTION AND GENETICS OF PORCINE INNATE

IMMUNE PROTEINS

INTRODUCTION

The innate immune system forms the first line of defense against pathogenic organisms. This ancient

and universal host defense system is intended to clear bacterial, fungal and viral infections before

intervention by the adaptive immune system. Antigen-presenting cells (APCs), such as macrophages

and dendritic cells (DCs), play a central role not only in the initial recognition and processing of

microbial antigens, but also in the subsequent activation of effector T and B cells (adaptive

immunity). Activation of APCs involves the interaction between pattern recognition receptors (PRRs)

in circulation as well as those expressed on cell surfaces, and within the cytoplasm of macrophages,

DCs and other cells of the innate immune system with pathogen-associated molecule patterns

(PAMPS) that are present on different groups of microbes and that are essential for their survival.

These PAMPs include lipopolysaccharide (LPS), peptidoglycan, lipoteichoic acids, mannose and

other sugar moieties, unmethylated CpG DNA, bacterial and protozoal proteins, dsRNA, ssRNA and

glucans. There are two major classes of PRRs: signalling receptors and endocytic receptors. The

binding of microbial products to signalling PRRs such as the Toll-like receptors (TLRs) and

nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) stimulates the

transcription and production of inflammatory cytokines, triggering innate immune defenses such as

inflammation. Endocytic PRRs promotes the attachment and subsequent engulfment/destruction of

microbes (Janeway 1989, Medzhitov 2009). In addition to PAMPs, many of these proteins also

interact with various danger associated molecular patterns (DAMPs), such as those generated during

cellular necrosis and oxidative damage of cells as well as extracellular ATP and potassium,

hyaluronan fragments, uric acid and heat shock proteins (HSPs). These interactions between PRRs

and DAMPS can further modify the inflammatory response (Mogensen 2009). The various TLRs,

collagenous lectins, galectins, macrophage scavenger receptors and C-type lectin receptors,

complement proteins, NLRs, retinoic acid-inducible gene I (RIG-1) like receptors (RLRs) as well as

peptidoglycan recognition proteins (PGLYRPs) and antimicrobial peptides (AMPs) all play important

5

roles in pathogen recognition and innate immune defense. The intent of this literature review is to

provide an overview of the structure, function and genetics of these various receptors and

antimicrobial molecules that constitute the porcine innate immune system.

6

TOLL-LIKE RECEPTORS

Toll-like receptors (TLRs) are one of the most widely studied components of the innate

immune system. These receptors play a central role in dorsal-ventral embryonic polarity in

Drosophila spp. and, for this reason, were initially referred to as Drosophila Toll transmembrane

proteins (Hashimoto et al. 1988). Shortly thereafter, it was discovered that the human genome, and the

genome of other mammalian species, contained sequences that were similar to the Drosophila TLR

genes. The finding that these receptors, referred to as hToll receptors (Medzhitov et al. 1997) and as

the human cytoplasmic Toll/IL1R homology (TIR) domain by Gay et al. (Gay and Keith 1991), had

potent antifungal properties (Lemaitre et al. 1996) and were able to recognize and bind microbial

PAMPs (Medzhitov et al. 1997) led to the concept that TLRs were important components of the

immune system. Since these initial studies, TLRs have been extensively studied and reviewed

(Eisenbarth and Flavell 2009, Lin et al. 2012, Takeda and Akira 2007, Takeuchi and Akira 2010,

Uenishi and Shinkai 2009).

TLRs are membrane-bound receptors that are localized on the cell-surface membrane and on

the plasma membrane of endolysosomes. To date, a total of 13 different mammalian TLRs have been

identified including 10 human and 10 porcine TLRs (TLR 1-10) and 12 murine TLRs (TLR 1-9 and

11-13) (Eisenbarth and Flavell 2009, Takeda and Akira 2007, Takeuchi and Akira 2010, Uenishi and

Shinkai 2009). Structurally, TLRs are arranged into three domains, an extracellular domain, a trans-

membrane domain and an intracellular or endolysosomal cytoplasmic Toll/IL1R homology (TIR)

domain. The N-terminal domain consists of 16 to 28 leucine-rich repeats (LRR), arranged in a

horseshoe shaped structure. This extracellular domain is responsible for the binding specificity of

each receptor (Uenishi and Shinkai 2009, Werling et al. 2009). The Toll-interleukin-1-receptor

homology (Toll/IL1R homology/TIR) domain, located on the cytoplasmic side of the cell membrane

(plasma membrane associated TLRs) and within the lysosomal compartment (endolysosomal

associated TLRs), interacts with several adaptor proteins. These adaptor proteins include myeloid

differentiation primary response gene 88 (MyD88), which contains a Death (DD) and TIR domain,

and a TIR-domain containing adaptor protein inducing IFN- (TRIF or TICAM-1) as well as the Toll-

7

interleukin 1 receptor (TIR) domain containing an adaptor protein (TIRAP/Mal), a TRIF related

adaptor molecule (TRAM), and a sterile-alpha and armadillo motif-containing protein (SARM)

(Mogensen 2009, Takeuchi and Akira 2010). These adaptor molecules are essential for effective

cellular signalling via TLRs.

The main cell membrane associated receptors are TLR1, TLR2, TLR4, TLR5, TLR6 and

TLR11. The endolysosomal associated TLRs include TLR3, TLR7, TLR8, TLR9 and TLR10. The

ligands recognized by these various TLRs have been identified and extensively reviewed. These

receptor-ligand interactions are dependent, in large measure, on the cellular localization of the specific

receptor. Ligands and cellular locations are summarized in Table 1.1 (Mogensen 2009, Takeda and

Akira 2007, Takeuchi and Akira 2010, Werling et al. 2009).

The ligands for TLR1 and TLR6 are triacyl- and diacyl-lipoproteins (bacteria and viruses)

respectively. Lipoproteins (bacteria, virus, and parasites) are the primary ligands for TLR2 (Yang et

al. 1998). Endotoxin, or lipopolysaccharide (LPS), a component of the cell wall of Gram-negative

bacteria, is the main TLR4 ligand. Activation of TLR4 occurs only in the presence of myeloid

differentiation protein-2 (MD-2), CD14 and lipopolysaccharide binding protein (LBP) and involves

homodimerization of TLR4 (Park et al. 2009). Other TLR4 ligands include the heat shock proteins

released during necrosis and cell death (Ohashi et al. 2000). Flagellin (flagellated bacteria) and

profilin (protozoa) function as ligands for TLR5 and TLR11, respectively.

TLR3 recognizes and binds the double stranded RNA (dsRNA) found in some viruses. In

contrast, TLR7 (and TLR8 in humans) binds single stranded RNA (ssRNA) found in viruses and

bacteria, as well as purine analog compounds such as imidazoquinolone. CpG DNA and the DNA

sugar backbone of 2′-deoxyribose (viruses, bacteria, protozoa) (Haas et al. 2008) are ligands for TLR9

(virus, bacteria, and protozoa). TLR9 is also activated by malaria after binding to hemozoin, this

results from direct interaction with hemozoin itself as well as malarial DNA bound to the hemozoin

molecule (Coban et al. 2010, Parroche et al. 2007). Recent reports have shown that TLR10 has similar

ligand binding characteristics to that of TLR1 (Guan et al. 2010). The murine receptor, TLR11, which

8

is absent in humans and other mammals, shows close homology to TLR5 (Yarovinsky et al. 2005). It

is uncertain whether this homology has any functional significance.

Specific signal pathways are activated by the interaction of a given ligand with its cognate

receptor. In some cases, binding is not sufficient to induce signaling. Structural changes in the TLR,

such as homodimerization or heterodimerization may also be required for signaling e.g. homo-

dimerization of TLR4 following binding of LPS and interaction with MD-2, homodimerization of

TLR3 after binding to N- and C-terminal ends of dsRNA, TLR1/2, TLR6/2 and TLR10/2

heterodimerization in association with formation of internal pockets (Guan et al. 2010, Ozinsky et al.

2000, Park et al. 2009). Apart from TLR3, MyD88 is involved in all TLR-mediated signalling. The

mechanism involves a sequential signaling cascade that leads to activation and nuclear translocation

of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) as well as the activation of

the three mitogen-activated protein kinase (MAPK) pathways: extracellular signal–regulated kinase

(Erk), Jun N-terminal kinase (Jnk) and p38. NF-κB controls the transcription of inflammatory genes,

and MAPKs regulate both the transcription of inflammatory genes and the stability of these mRNA

transcripts. MyD88-independent/TRIF-dependent signaling (unique to TLRs 3 and 4) leads to the

production of interferon (IFN)-ß (Han 2006, Mogensen 2009, Takeda and Akira 2007).

The porcine genes encoding TLRs 1, 2, 6 and 10 are found on chromosome 8 (SSC8). A

putative quantitative trait locus (QTL), related to the immune properties of TLRs 1, 6 and 10 has also

been identified on this chromosome and is located in a cluster on the p arm (Muneta et al. 2003). In

humans these three TLRs have also been shown to be genetically related likely representing gene

duplication events (Guan et al. 2010). Despite the observed genetic similarities; TLR10 activated

signaling pathways have been shown to differ from those observed for TLR1 and TLR6 (Guan et al.

2010). TLR10 also requires heterodimerization with TLR2 to initiate signal transduction and likewise

to other TLRs also involves MyD88 mediated signalling (Guan et al. 2010, Hasan et al. 2005). In

contrast however to other TLRs, TLR10 signaling does not result in NF-κB-, IL-8-, or IFN-ß-driven

responses and further characterisation of these pathways are necessary to better understand the role

that TLR10 plays as a PRR (Guan et al. 2010, Hasan et al. 2005, Shinkai et al. 2006). In the mouse,

9

TLR10 is disrupted by an endogenous retrovirus and exists as a pseudogene (Guan et al. 2010). The

functional loss of this gene in the mouse has not been associated with any consequence to host

defense and the exact function of this TLR10 remains obscure. Similar QTL sequences are also found

at the distal end of the q arm of SCC8 within the region adjacent to the TLR2 gene (Bergman et al.

2010, Jann et al. 2009, Shinkai et al. 2006). The presence of these QTL’s underscores the importance

of these TLRs in the host immune response.

Non-synonymous SNPs are common in the extracellular LRR domain of all TLRs, especially

in swine (Morozumi and Uenishi 2009, Shinkai et al. 2006, Uenishi et al. 2011). There is considerable

species-specific variation in these SNPs and in the selection pressure exerted on the ligand binding

domain of TLRs (Bergman et al. 2010, Morozumi and Uenishi 2009, Shinkai et al. 2006, Uenishi and

Shinkai 2009). Numerous SNPs have been identified in the cell membrane/ectodomain of various

membrane-bound human and porcine TLRs as well as in the endosomal/lysosomal domain of TLRs in

cattle (Uenishi and Shinkai 2009, Werling et al. 2009). In one study, a total of 136 SNPs (45, 23, 13,

35, and 20) were identified in five different porcine TLR genes (TLR1, TLR2, TLR4, TLR5, and TLR6

respectively), 63 of which result in amino acid substitutions (Shinkai et al. 2006). The majority of

these non-synonymous SNPs were present in the LRR regions of the ectodomain, especially in the

genes that code for TLRs 1, 2 and 6 (Shinkai et al. 2006, Uenishi and Shinkai 2009). The levels of

heterozygosity among non-synonymous SNPs found in the TLR1 and TLR6 genes were greatest in the

regions encoding for the first four LRRs and the 13th LRR proximal to the C-terminal domain. In

contrast, synonymous SNPs with high levels of heterozygosity were located in LRRs 9-12 (Shinkai et

al. 2006, Uenishi and Shinkai 2009). The high degree of variability of these SNPs within the LRR

domains has been proposed to broaden both the range of ligand recognition and thus the ability of

these receptors to recognise a large variety of pathogens. In contrast few SNPs are found in the

domains related to signal transduction and downstream signaling pathways. Such SNPs are believed

to be deleterious and thus, may have been eliminated through evolutionary selective pressure (Uenishi

and Shinkai 2009, Uenishi et al. 2011). Interestingly, non-synonymous and synonymous SNPs in

TLR1, 2 and 6 are far less common in European wild boar populations compared to domestic pigs. As

10

mentioned previously, this difference may be due to increased selection pressure as a consequence of

domestication (Bergman et al. 2010). In the Bergman study; 20, 27 and 26 SNPs were identified in the

TLR1, TLR2 and TLR6 genes of domestic pigs, respectively. Of these SNPs, one major high frequency

haplotype was detected in each of the three genes found in three different European wild boar

populations compared with one high frequency haplotype in the TLR2 gene of the studied domestic

pigs. The relative frequency of non-synonymous SNPs to synonymous SNPs was lower in all three

genes of the wild boar population than in domestic pigs, in this case possibly being a reflection of the

detrimental effects of non-synonymous SNPs on TLR function and ligand specificity.

To date, very few non-synonymous SNPs have been detected in the ectodomain of the porcine

TLR4 gene (Uenishi and Shinkai 2009). In one study, 34 SNPs, 17 in the coding sequence and 17 in

the non-coding sequence including the promoter region were identified. Five of the non-synonymous

SNPs were found to cluster within, or were located in close proximity to, the hyper-variable domain

in exon 3. As in other mammalian species a major exon 3 haplotype can be identified with non-

synonymous SNPs in this region only being present at low frequencies (ranging from 0.6 % and 8.7

%) (Palermo et al. 2009). Different polymorphism in the TLR4 gene has also been shown to have

different frequencies in Japanese wild boar populations when compared to domestic pigs; this is

presumably due to evolutionary selective pressure due to varying residential pathogens or

demographic factors (Shinkai et al. 2012). SNPs are uncommon in the cytoplasmic TIR domain

(dimerization or signaling domains) and sequences in this region are highly conserved across

mammalian species (Bergman et al. 2010, Uenishi et al. 2011, Werling et al. 2009).

The genes encoding endosomal TLRs (TLR3, 7, 8 and 9) of pigs are also highly conserved

with far fewer reported SNPs than in cell surface TLRs, however genetic variations are similarly

distributed and more common within the ectodomain. This relative lack of polymorphisms within the

LRR domains of endosomal TLRs suggests that nucleic acid recognition and binding is well

conserved and a higher degree of variability within the LRR domains may in fact be detrimental to

these PRRs (Morozumi and Uenishi 2009, Uenishi and Shinkai 2009, Uenishi et al. 2011). Porcine

TLR10 has recently been reported to contain more SNPs relative to other TLRs with 13 synonymous

11

and 20 non-synonymous SNPs being detected in a small sample size of 30 pigs (15 wild boar and 15

pure bred Landrace, Hampshire and Large white) (Bergman et al. 2012). Once again, wild boars

contained fewer SNPs and fewer SNP haplotypes than domestic pigs. Bovine TLR4 was found to be

highly polymorphic with seven SNPs being reported (Zhou et al. 2007). Eleven SNPs have been

detected in the TLR4 gene of sheep (Zhou et al. 2007) and five non-synonymous SNPs have been

identified in the extracellular domain of the TLR4 gene in chickens (Leveque et al. 2003). A mutation

in murine TLR4 was originally identified in mice resistant to LPS resulting in substitution of proline

with histadine at position 712 in the amino acid sequence (Poltorak et al. 1998). Subsequently it was

also shown that mutational changes to the structure and expression of TLR4 resulted in variation in

sensitivity to LPS (Du et al. 1999). Two SNPs located within the coding region of the extracellular

domain of the human TLR4 gene, A(896)G [Asp299Gly)] and C(1196)T [Thr399Ile], are associated

with a decreased ability to respond to LPS either as a result of altered binding capacity or altered

ligand induced homo-dimerization (Arbour et al. 2000, Rallabhandi et al. 2006). The presence of

these SNPs has also been linked to an increased risk of acquiring several infectious and non-infectious

diseases (Arbour et al. 2000, Rallabhandi et al. 2006, Schroder and Schumann 2005, Yamakawa et al.

2013). In contrast, the presence of these SNPs can have a protective role in cases where the immune

response to circulating LPS is detrimental (Senthilselvan et al. 2009). SNPs in the human TLR2 gene,

G(2251)A [Arg753Gln] and C(2029)T) [Arg677Trp], have been reported to reduce immune

responsiveness to a number of pathogens and disease syndromes (Ben-Ali et al. 2004, Lorenz et al.

2000, Pabst et al. 2009, Schroder et al. 2003). Some of these changes appear to be due to impaired

ligand binding. Many other human TLR SNPs have been identified but their disease associations have

not been well characterized (Arbour et al. 2000, Arbour et al. 2000, Rallabhandi et al. 2006,

Rallabhandi et al. 2006, Uenishi and Shinkai 2009). Very few disease association studies have been

performed in pigs and the pathological significance of most SNPs is still unknown. SNPs in the TLR2

and TLR6 genes can alter the heterodimerization process and/or function of these receptors. It has

been suggested that these changes may play an important role in Mycoplasma hyopneumoniae

infection (Muneta et al. 2003, Uenishi et al. 2011) and putatively, other diseases. Keirstead et al.

detected an increased frequency of the TLR1 C(2305)T and TLR5 C(1919)A SNPs in diseased pigs

12

with pneumonia, septicemia and enteritis. A 3-fold increase in the frequency of the TLR5 C(1919)A

was detected in pigs with PRRSV and PCV-2 and a 5-fold increase was observed in pigs diagnosed

with Streptococcus suis (Keirstead et al. 2011). The association between increased TLR5 C(1919)A

and infection with PRRSV and PCV-2 was unexpected as bacterial flagellin is the major ligand of

TLR5. This may be due to co-linkage of the TLR5 C(1919)A SNP with other SNPs or to variations in

factors involved in antiviral signaling. Further studies are needed to clarify this apparent discrepancy.

13

COLLECTINS AND FICOLINS (COLLAGENOUS LECTINS)

Collectins (CL) and ficolins (FCN) are multimeric proteins that recognize sugar moieties and

are often grouped together as collagenous lectins, because both share a similar collagen-like domain

as one of their key features. These components of the innate immune system are found in a number of

vertebrate and invertebrate species (Table 1.2). They were first described as plant proteins that had the

capacity to agglutinate erythrocytes. Conglutinin (CG/COLEC8), the first was identified in 1906

(Bordet and Streng 1909, Holmskov and Jensenius 1993, Holmskov et al. 1994). More recently with

renewed interest in innate immunity and PRRs, they have received significant attention. Many

microbial targets on bacteria, viruses, fungi and protozoa that interact with these sugar-binding lectins

have been identified and are described in detail in several reviews (Holmskov et al. 2003, Ip et al.

2009, Keirstead et al. 2008, Kuroki et al. 2007, Lillie et al. 2005, Turner 2003, Veldhuizen et al.

2011). Collagenous lectins function as receptors for pathogen recognition and are involved in

phagocytosis, opsonisation/agglutination and complement activation. Apart from CG, this group

includes proteins such as mannan-binding lectin A (MBL-A), mannan-binding lectin C (MBL-C),

surfactant protein A (SP-A), surfactant protein D (SP-D), collectin liver 1 (CL-L1), collectin placenta

1 (CL-P1), collectin of 43 kDa (CL-43/COLEC9), collectin of 46 kDa (CL-46/COLEC13), collectin

kidney 1 (CL-K1), as well as multiple ficolins, whose nomenclature varies in different species.

Proteins in the collagenous lectin group of receptors are oligomeric assemblies of multiple

trimeric proteins composed of three identical monomer polypeptide units, except for surfactant

protein-A (SP-A), which contains three almost identical units (Holmskov et al. 2003). Each monomer

can be divided into four domains: an N-terminal cysteine rich domain followed by a collagen-like

region of glycine-X-Y (Gly-X-Y) repeats, a neck domain and a C-terminal globular carbohydrate

recognition domain (CRD). The N-terminal cysteine rich domain is important for disulfide bridging

(Cys24

-Cys24

) between adjacent monomers and for trimer stabilization (Holmskov et al. 2003, Jensen

et al. 2005, Ohashi and Erickson 2004). This region is critical for higher order oligomerization with a

minimum of two disulfide bonds being required for efficient oligomer formation (Jensen et al. 2005,

Phatsara et al. 2007). The Gly-X-Y repeat region contributes to the coiled-coil appearance and tertiary

14

structure of the basic trimeric unit (Colley and Baenziger 1987, van Eijk et al. 2000). In addition, the

collagen-like domain contains a six amino acid sequence, GEKGEP, which is similar to sequences

observed in the human and murine C1q with some variation in the third amino acid position (arginine

or glutamate replacing lysine). GEKGEP interacts with C1qRp on leukocytes and plays an essential

role in lectin-mediated phagocytosis (Arora et al. 2001). The GEKGEP sequence is absent in

surfactant protein-D (SP-D) and all mammalian FCNs expect for porcine FCN-α and FCN-β;

suggesting that in pigs, FCNs may play a role in lectin-mediated phagocytosis (Ichijo et al. 1993).

Within the collagen-like domain of CLs, there is a structural interruption, called the Gly-X-Gly

kink/interruption, which provides structural flexibility and allows for higher order sertiform structure

formation (van de Wetering et al. 2004). Although, on electron microscopy, a similar structural bend

is observed in ficolins, it is not due to the presence of a Gly-X-Gly motif kink as in collectins (Ohashi

and Erickson 1997, Ohashi and Erickson 1998). An MBL associated serine protease (MASP)–binding

motif containing hydroxyproline, (Hyp)-Gly-Lys-X-Gly-Pro is located within the collagen-like

domain on the C-terminal side of the Gly-X-Gly kink (Schwaeble et al. 2002, Walport 2001, Zuo et

al. 2010). This sequence is relatively conserved across all mammalian MBLs (Wallis et al. 2004) with

the exception of porcine MBL-C where Met is substituted for Lys, a substitution that has no apparent

effect on MASP binding and subsequent complement activation (Agah et al. 2001). This same

sequence is also present and highly conserved in porcine, rodent and primate ficolins but with certain

amino acid substitutions (specifically Glu for Lys and Val for Hyp in porcine FCN-α and -β

respectively) (Schwaeble et al. 2002, Wallis et al. 2004, Walport 2001). The neck domain is a

relatively short region that functions to line up the collagen-like domains and facilitate formation of

the collagen triple α-helix (Lillie et al. 2005).

The C-terminal end of collectins is characterized by the presence of a large globular

carbohydrate recognition domain (CRD), with binding being calcium dependent (Holmskov and

Jensenius 1993). In contrast, the CRD of ficolins is fibrinogen-related with binding taking place

independent of calcium. All collectins with the exception of collectin placenta 1 (CL-P1) bind

mannose, glucose and other monosaccharides that contain a hydroxyl group in the equatorial plane at

15

carbon atoms 3 and 4 of the pyranose ring (Lee et al. 1991, Ng et al. 1996, Weis et al. 1992). The

sugar binding specificity of CLs is determined by a three amino acid consensus sequence in the CRD

(Ng et al. 1996). Collagenous lectins with the Glu-Pro-Asn sequence bind mannose-type sugars (Weis

et al. 1992), while those with Gln-Pro-Asp bind galactose-containing sugars (Ohtani et al. 2001). The

fibrinogen-related CRD of FCN binds N-acetyl-D-glucosamine (GlcNAc) (Ohashi and Erickson

1997) and other acetylated compounds (Brooks et al. 2003a, Brooks et al. 2003b, Krarup et al. 2004).

Collectin liver 1 (CL-L1) contains a serine substitution (Glu-Pro-Ser), but the impact of this

substitution on sugar binding has not been studied (Ohtani et al. 1999). The various lectin sugar

ligands are summarized within Table 1.2.

Higher order oligomerization of the basic trimeric subunits occurs in all collectins with the

exception of CL-43 and CL-L1 which exist as a basic trimeric unit (Colley and Baenziger 1987,

Holmskov et al. 2003, Ohashi and Erickson 2004, van Eijk et al. 2000). Ficolins, CG, MBLs and SP-

D form tetra-trimers while SP-A and C1q form hexa-trimers (Ohashi and Erickson 2004). Higher

order oligomerization increases the binding avidity of sertiform and cruciform oligomers, from 10-3

M

as a single CRD to 10-10

M in higher oligomers (Lee et al. 1991). Binding specificity is also affected

by saccharide composition and the spatial relationships between CRDs in cell membranes (Hoffmann

et al. 1999). MBLs, SP-A and FCNs form sertiform oligomers (Holmskov et al. 2003, van de

Wetering et al. 2004) while SP-D, CG and CL-46 form cruciform oligomers (Holmskov et al. 2003).

CL-P1 is a membrane-bound trimer originally identified in endometrial tissue (Lillie et al. 2005).

Cruciform lectins (SP-D, CG and CL-46) and SP-A (sertiform lectin) play a role in pathogen

recognition, opsonisation and agglutination while other sertiform lectins (MBLs and FCNs), although

also having opsonisation and agglutination capabilities, primarily interact with MASPs (1, 2, 3) and

the MBL-associated proteins, MAp19 or sMAP (Lawson and Reid 2000, Schaeffer et al. 2004, van de

Wetering et al. 2004). This leads to activation of the complement cascade and the clearance of

targeted PAMPs (Endo et al. 2007, Fujita et al. 2004b, Fujita et al. 2004b, Schwaeble et al. 2002,

Walport 2001). There are three different MASPs proteins, MASP-1, -2 and-3. These molecules are

analogous in structure and function to the C2 and C4 cleaving C1r and C1s serine proteases of the C1

16

complex (Schwaeble et al. 2002, Walport 2001). MASP-2 exhibits a 3- and 23-fold increased ability

to cleave C2 and C4 respectively, relative to human C1s suggesting that MASP-2 is a potent mediator

of complement activation (Rossi et al. 2001). Another recent study has suggested that ficolins may

also be capable of inducing MASP associated complement activation (Girija et al. 2007). Collagenous

lectins also play a role in sensing DAMPs and MBL has been implicated to play a major role in

reperfusion injury (Diepenhorst et al. 2009).

Collagenous lectins such as MBLs and FCNs are present circulating in plasma and are

expressed predominantly in the liver but also at mucosal surfaces. In the pig, FCNs are also expressed

in neutrophils (FCN-β) (Brooks et al. 2003c) and cells of the endometrium (Ichijo et al. 1993) and

immuoreactive FCNs have been shown to be present within the intestinal crypt and lung epithelium

(De Lay 1999). However it is unclear if expression takes place at these sites as well. The genes coding

for these receptors are relatively conserved across the animal kingdom (Holmskov et al. 2003, Lu et

al. 2002, Phatsara et al. 2007, van de Wetering et al. 2004). In pigs SP-A, SP-D and MBL-A are

located within the collectin locus (syntenic genes) on chromosome 14; similar to humans, cattle and

mice (Gjerstorff et al. 2004, Marklund et al. 2000, van Eijk et al. 2000, van Eijk et al. 2002). In

humans, the MBL2 gene (MBL-C) contains four exons: exons 1 and 2 encode the Gly-X-Y triple

collagen helix motif that forms the stalk; exon 3 the coiled-coil neck region and exon 4 the CRD

domain (Garred et al. 2006). The human L-ficolin gene (FCN2) contains sequences for a 25 amino

acid signal peptide and N-terminal region consisting of nine amino acids (exon 1and 2), a collagen-

like domain (exon 3), a neck region (exon 4), the first part of a fibrinogen-like domain (exons 5 to 7)

and the remaining portion of the fibrinogen-like domain (exon 8) (Endo et al. 1996). The human M-

FCN gene (FCN1) is organized in this same manner but contains an extra exon that codes for four

additional Gly-X-Y repeats (Endo et al. 2004, Endo et al. 2006, Endo et al. 2007). All mammals have

two MBL genes, MBL1 and MBL2, which corresponds to MBL-A and MBL-C respectively. Birds

(chickens) and fish have only one MBL gene. Humans and higher order primates have acquired a stop

codon in the gene encoding MBL-A, resulting in the expression of a pseudo gene referred to as

MBL1P (Guo et al. 1998, Lillie et al. 2005, Phatsara et al. 2007). Ascidians and frogs have multiple

17

FCNs. Humans and non-human primates have three FCNs, M-FCN (FCN1), L-FCN (FCN2) and H-

FCN (FCN3) while chickens have only one FCN. Some mammals have two sets of related FCNs

(FCN-α and -β in pigs, FCN-A and -B in rodents; both encoded by FCN1 and FCN2 and FCNA and

FCNB respectively) (Endo et al. 2006, Endo et al. 2007, Fujita et al. 2004a, Fujita et al. 2004b,

Kakinuma et al. 2003, Kenjo et al. 2001, Lillie et al. 2005). In rodents (mice and rats), FCN3 exists as

a pseudo gene (Endo et al. 2004). There are two basic groups of mammalian FCNs: a circulating

plasma group that includes pig FCN-α, mouse FCN-A and human and primate L-FCN and a group

that is present in peripheral blood monocytes, neutrophils and cells of the bone marrow, lung and

spleen. This second subset includes pig FCN-β, mouse FCN-B and human and primate M-FCN (Endo

et al. 2007). The species distribution of the various collagenous lectins is summarized in Table 1.2.

Several different SNPs have been detected in the CL and FCN genes of humans and other

mammalian species (Crouch et al. 1993, Garred et al. 2003, Garred et al. 2006, Juul-Madsen et al.

2011, Lahti et al. 2002, Lillie et al. 2005, Lillie et al. 2006, Lillie et al. 2007, Lipscombe et al. 1992,

Madsen et al. 1994, Madsen et al. 1998, Marklund et al. 2000, Phatsara et al. 2007, Sumiya et al.

1991, Wang et al. 2011, Zhou et al. 2010). These polymorphisms can be divided into SNPs in the

coding region (that affect the structural characteristics of collagenous lectins) in the promoter region

(that may affect gene expression) those present in non-coding or intronic regions, and synonymous

coding region SNPs (that may or may not alter gene expression without resulting in changes to the

structural/functional properties of collagenous lectins).

Nine different SNPs have been identified in the non-coding regions of the porcine MBL2. One

of these SNPs, a C to T substitution at position 328 in the intronic region is associated with the loss of

an HinfI restriction site (Lillie et al. 2007, Marklund et al. 2000, Phatsara et al. 2007). Five SNPs are

found in the promoter region of MBL2 at positions -2148 (T to C), -1081 (G to A), -1636(T to G), -

1614(A to G) and -251 (C to T) (Keirstead et al. 2011, Lillie et al. 2007). All of these SNPs, with the

exception of C(-251)T, are present at increased frequencies in pigs with pneumonia, septicemia,

enteric disease and serositis and in pigs infected with specific etiologic agents such as Streptococcus

suis, porcine reproductive and respiratory syndrome virus (PRRSV) Salmonella enterica subsp.

18

enterica ser. Typhimurium (S. Typhimurium), porcine circovirus type 2 (PCV2), Escherichia coli and

Mycoplasma spp.) (Keirstead et al. 2011, Lillie et al. 2007).

There are three well-known mutations in the promoter region of the human MBL2 gene: H/L

[G(-550)C], X/Y [G(-221)C] and P/Q at (position +4 in the 5'UTR). These SNPs are associated with

decreased serum levels of MBL-C (Garred et al. 2003, Madsen et al. 1998). In humans, three non-

synonymous MBL2 SNPs, located within exon 1, results in amino acid substitutions in codon 52 (Arg

to Cys - D allele), 54 (Gly to Asp - B allele) and 57 (Glu to Gly - C allele) (Garred et al. 2003, Garred

et al. 2006, Lillie et al. 2005, Lipscombe et al. 1992, Madsen et al. 1994, Madsen et al. 1998, Phatsara

et al. 2007, Sumiya et al. 1991). All three SNPs are associated with destabilization of the collagen

triple helix and result in a marked reduction in serum levels of MBL-C (Garred et al. 2003, Garred et

al. 2006). Numerous MBL2 promoter SNPs and infectious diseases studies have been performed in

humans and disease associations have been firmly established (Hamvas et al. 2005, Mullighan et al.

2002, Thiel 2007, Zhang et al. 2005, Zhang and Ali 2008). The human MBL1P1 pseudo gene

contains an intron 1 splicing defect, in addition to two nonsense mutations in exon 3 and 4 and a Gly

to Arg substitution in codon 53. The latter substitution is proposed to disrupt the collagen backbone of

the protein in analogy to the human MBL2 codon 54 Gly to Asp substitution (Seyfarth et al. 2005).

Lillie et al. described three SNPs in the coding regions of the porcine MBL1 gene: G(271)T;

C(273)T and C(687)T SNPs. Two of these SNPS, C(273)T and C(687T) are synonymous mutations.

The remaining SNP, G(271)T, is a non-synonymous mutation located in the collagen-like domain of

the gene. This mutation is similar to both the human MBL2 B/C and the D allele variants in that it

results in the replacement of a glycine to cysteine residue. By analogy to the human gene, this

substitution may also disrupt the collagen structure and its structural stability and alter the blood

levels of the MBL1 gene product (Garred et al. 2006, Garred et al. 2006, Juul-Madsen et al. 2006,

Juul-Madsen et al. 2011, Lillie et al. 2006). Increased frequencies of C(273)T and C(687)T have been

detected in all diseased pig groups (with the exception of those with serositis) (Keirstead et al. 2011)

and in pigs diagnosed with Escherichia coli, Haemophilus parasuis, Actinobacillus

pleuropneumoniae and Streptococcus suis infections. An intronic SNP, MBL1 C(int)T, has also been

19

detected in diseased pigs with enteritis and pneumonia syndromes (Keirstead et al. 2011, Marklund et

al. 2000). How this intronic SNP is related to gene and protein function is, however, still not clear.

The mean serum concentration of MBL-A is a heritable characteristic of Danish Landrace

pigs but not Duroc pigs (Juul-Madsen et al. 2006). Recent studies by Juul-Madsen et al. (2011) have

described 14 different SNPs in the porcine MBL1 gene, eight in exons and six in introns. Four of the

exon SNPs were non-synonymous (A(77)G, C(161)G, T(871)C and G(949)T); the remaining four

were synonymous and located at positions 30, 951, 3233 and 3344. The six intron SNPs were found at

positions 193, 216, 488, 1046, 1102 and 1103. One set of MBL1 SNP haplotypes (A2) was associated

with a decrease in serum concentrations of MBL-A which is likely due to a T substitution at position

949 (Juul-Madsen et al. 2011). This SNP is identical to the G(271)T SNP previously described (Lillie

et al. 2006).

Synonymous SNPs were also found at position G(579)A and G(645)A of the MBL2 gene

(Lillie et al. 2007). Three SNPs; G(855)A, G(2651)A and T(2686)C; have recently been identified in

the MBL1 gene of Chinese native cattle (Wang et al. 2011). G(855)A resides in intron 1, the other two

SNPs, one synonymous and one non-synonymous reside in exon 2. A significant association was

found between the G(2651)A SNP and the somatic cell count in these cows. The combined genotypes

of GGC/AAC had the lowest somatic cell count, AAT/AAT had the highest protein content and

AGC/AGC had the highest 305-day milk yield. These genotypes were considered favorable

combinations for resistance to mastitis and milk production traits (Wang et al. 2011). These findings

demonstrate the potential for SNP-based selection panels for improving innate disease resistance to

common diseases, as well as increased production and enhanced performance parameters. However,

multiple SNPs in the same genotype could affect expression or function in different directions, and

innate immune gene redundancy could mask the impact of particular SNPs. This means that large

panels of many functional SNPs and appropriate disease resistance phenotypes will be needed to

exploit this knowledge.

20

Keirstead et al. discovered three non-synonymous SNPs in the coding region of the CRD of

the SFTPA gene (SP-A). One of these SNPs, T(599)A, was associated with disease conditions such as

pneumonia, septicemia, enteric disease and serositis and with several bacterial infections (S. suis, H.

parasuis, E. coli, S. Typhimurium and Mycoplasma spp.) and the viral agents, PCV2 and PRRSV. No

disease associations were detected with three non-synonymous SNPs located in FCN1 and FCN2

(Keirstead et al. 2011). Several SNPs have been reported in the collagen-like domain of human SP-A

and SP-D with the SP-D SNPs at positions 11 (Met/Thr), 160 (Ala/Thr) and 270 (Ser/Thr) proposed to

result in structural changes to the protein (Crouch et al. 1993, DiAngelo et al. 1999, Heidinger et al.

2005, Lahti et al. 2002, Leth-Larsen et al. 2005) . Numerous disease association studies of these SNPs

have been performed in humans; however few such studies have been performed in pigs (Pastva et al.

2007, Sorensen et al. 2007).

21

C-TYPE LECTIN RECEPTORS AND SCAVENGER RECEPTORS

A number of other collectin-like receptors (CLRs) have been identified including dectin-1, -2

and -3, macrophage C-type lectin (MINCLE), pulmonary macrophage scavenger receptor (MARCO)

and DC-SIGN, a transmembrane receptor expressed on dendritic cells (DCs) and macrophages.

Dectins are immune receptors that contain a tyrosine based activation motif (ITAM) coupled to type II

membrane receptors. They are expressed on cells of myeloid origin (DCs, macrophages/monocytes

and neutrophils). Dectins recognize 1,3 and β1,6 linked glucans present in fungi, plants and bacteria

(Robinson et al. 2009, Zhou et al. 2010). MINCLE, a dectin expressed on macrophages, interacts with

fungi such as some Mallasezia and Candida (Yamasaki et al. 2009) as well as endogenous danger

associated molecular patterns (DAMPs) (e.g. spliceosome-associated protein 130 (SAP130))

(Yamasaki et al. 2008). Microbial binding to pulmonary macrophage scavenger receptor (MARCO)

and dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) results

in suppression of the expression of pro-inflammatory cytokines while increasing the expression of

NF- B through interaction with various TLRs (Geijtenbeek and Gringhuis 2009, Mukhopadhyay et

al. 2011) and nucleotide-binding oligomerization domain receptors (NLRs) (Mukhopadhyay et al.

2011). Please see Table 1.3 for a summary of the ligands and cellular localization of the C-type lectin

receptors (CLRs) and scavenger receptors.

To date, a total of nine SNPs have been identified in the -glucan domain of the ovine dectin-

1 gene, CLEC7A; all are present in exons 4 to 6. Four of these SNPs, in exons 4 (n = 2) and 6 (n = 2),

were found to be non-synonymous (Zhou et al. 2010). This gene exhibits a high level of homology

among sheep, cattle and pig populations, however no SNPs have been found in this gene in pigs or

cattle.

No disease or functional associations have been reported in the dectin-1 gene of pigs or other

livestock species (Zhou et al. 2010).

22

GALECTINS

Galectins were previously known as S-type lectins because of the presence of sulfhydryl or

thiol groups and the requirement for reducing conditions to maintain function. This now holds true

only for galectin-1 and -2 (Yang et al. 2008). Fifteen galectins have been identified in mammals and,

based on their structural features; they can be divided into three groups: prototype, tandem and

chimeric type galectins (Liu and Rabinovich 2010, Rapoport et al. 2008, Sato et al. 2009, Vasta 2009,

Yang et al. 2008). Prototype galectins have a molecular weight of approximately 14 kDa and contain

a single CRD. They exist as monomers (galectin-5, -7, -10 and -14), non-covalent dimers the result of

interactions between hydrophobic regions in the carbohydrate binding grooves located at opposite

ends of the CRD (galectin-1, -2, -7, -11, -13 and -14) or as homodimers (galectin-13) that are

stabilized by two disulfide bonds. Tandem type galectins contain two CRDs (homologous but not

identical in amino acid sequence) connected by a linker peptide that consists of 25 to 35 amino acid

residues enriched in proline and glycine tandem repeats (galectin-4, -6, -8, -9 and -12) (Rapoport et al.

2008, Sato et al. 2009, Yang et al. 2008). The chimeric type galectin-3 contains a single CRD with

one regulatory domain within the N-terminus. Furthermore galectin-3 consists of a 100-150 amino

acid sequence which is rich in glycine, tyrosine and proline residues and also contains a number of

repeated collagen-like regions. The active binding site of the CRD is formed by three peptide chains,

S4 to S6. The CRD oligomerizes and forms pentamers upon binding its cognate carbohydrate ligand,

a process that takes place through self-assembly of the N-terminal regulatory domain (Liu and

Rabinovich 2010, Sato et al. 2009, Vasta 2009, Yang et al. 2008). The globular region of the CRD

consists of two antiparallel -sheets composed of up to 130 amino acids containing six (S1-S6) and

five (F1-F5) peptide chains; respectively. Chain S3-S6 forms two long finger like projections that are

steeply bent forming a carbohydrate binding groove with five binding site regions labeled A to E. Site

C and D, the main binding sites, recognize lactosamine fragments. The hydroxyl (OH) group at the C-

4 site is considered crucial for carbohydrate binding. Sites A and B recognize fragment X and site E

recognizes fragment Y in the lactosamine chain structure. The -jelly roll accounts for the topology of

this region (Rapoport et al. 2008, Sato et al. 2009, Yang et al. 2008).

23

Galectins are located intracellular, in the cytoplasm and/or nucleus, and on the cell

membrane. Galectins 1-3 and 6-9 are found in a variety of different epithelial and endothelial cells as

well as various immune cells while galectin-4 and -7 are restricted to the epithelium of the digestive

tract (Wooters et al. 2005) and stratified squamous epithelium, respectively (Sato et al. 2009).

Galectin-1, -3, -9 and -12, are found in all cells of the immune system (Sato et al. 2009). A number of

different cell populations contain galectins-5 and 10-14 (Rapoport et al. 2008). These lectins are

produced through a non-classical synthetic pathway that bypasses the endoplasmic reticulum (ER)

and Golgi apparatus. Following synthesis in cells such as keratinocytes, fibroblasts, endothelial cells

and mucosal epithelial cells, galectins are stored in exosomal vesicles that subsequently fuse with the

cell membrane during times of stress (inflammation or malignant transformation) (Rapoport et al.

2008, Sato et al. 2009). Alternatively, they can be released directly from damaged cells (Elola et al.

2007).

The CRD of galectins binds galactose residues that are linked to an adjacent monosaccharide

in the -configuration ( -galactoside/ Gal 1,4GlcNAc) (Elola et al. 2007, Sato et al. 2009). Binding is

calcium independent with the specificity of binding being determined by a hydroxyl group on residues

C-4 and C-6 (with the C-4 OH being the most critical) and on a GlcNAc residue located at position C-

3 of the sugar moiety (Rapoport et al. 2008, Sato et al. 2009). The target galactose molecules are often

found in O-linked and N-linked “complex type” glycoproteins. Binding avidity is increased through

multivalent interactions with the ligand and is affected by temperature (i.e. membrane fluidity).

Glycan clusters or ordered arrays formed of lectin and multivalent glycoconjugates are often referred

to as the glycan lattice (Sato et al. 2009, Yang et al. 2008). This glycan lattice may prevent

endocytosis of the bound ligand and thereby, prolong the signal transduction. (Sato et al. 2009).

Interactions between galectin PRRs and microbial pathogens have been extensively reviewed

(Sato et al. 2009, Vasta 2009). Intracellular galectins have been shown to play a role in cell cycle

regulation by either inducing or suppressing apoptosis and modulating cellular proliferation and

differentiation. Galectins-1 and -3 bind to Ras proteins and stimulate the Raf - PI3K pathway leading

to mitogenic activity. Bcl-2 contains a binding site for galectin-3 and binding abolishes the anti-

24

apoptotic binding activity of the lectin. Galectins-1 and -7 are positive regulators of apoptosis but the

exact mechanism is unknown although galectin-7 appears to play a role in FAS/caspase-8

mechanisms (Rapoport et al. 2008, Yang et al. 2008). Galectin-1 enhances the expression of

interferon gamma receptor (IFN R) on T-lymphocytes (Rapoport et al. 2008). Intracellular galectins

activate cyclin dependent kinases through an unknown mechanism. Galectins-3 and -12 have been

shown to inhibit cyclin E, A and D1, arresting the cell cycle in the G1-phase. They have also been

implicated in the regulation of gene transcription via specificity protein 1 (Sp1) transcription factor

and cAMP response element-binding (CREB) (Rapoport et al. 2008). Of importance, is their ability to

interact with cellular proteins that regulate galectin transport and expression of galectins on the cell

surface. Surface membrane galectins play a role in cell-cell and cell-matrix adhesion as well as

regulation of the immune system during inflammation and oncologic transformation (Rapoport et al.

2008). Cell-cell and cell-matrix binding takes place via polylactosamine chains of glycoproteins and

is dependent on the concentration of resident galectins, as well as, interactions with cellular

differentiation factors, a process that can have both positive and negative effects on cell adhesion.

Interaction with the carbohydrate chains of integrins, intercellular matrix proteins and membrane

glycolipids induces a cascade of signaling reactions that control cell proliferation and apoptosis

(Rapoport et al. 2008). Galectins can induce apoptosis of T-lymphocytes through interaction with N-

glycans of proteins and subsequent exposure to phosphatidyl-serine as observed with galectin-1 with

CD45, CD43 and CD7; galectin-3 with CD29, CD7 and CD95; and galectin-2 with 1-integrin (Liu

and Rabinovich 2010). Galectins also induce phagocytosis by scavenging immune system cells

(lectin-mediated phagocytosis). Galectin-3 binds to N-glycan LacdiNAc fragments of helminthic cells

and apoptotic bodies of macrophages. Galectin-3 and -9 act as potent chemo attractants for

neutrophils and eosinophils respectively with both galectin-1 and -3 playing a role in neutrophil

adhesion and trafficking (Liu and Rabinovich 2010). Apart from the important role, these proteins

play in sensing PAMPs, galectins like other PRRs have also been proposed to interact with DAMPs

released during tissue injury (Sato et al. 2009).

25

Very little is currently known about the genetics of galectins. The structural features and

genes coding for these lectins seem to be strongly conserved across all species (Vasta 2009). Few

genetic studies have been performed and concrete disease associations are not available (Sato et al.

2009, Vasta 2009). Keirstead et al. discovered four novel polymorphisms within the gene encoding

for porcine galectin 4 and all were located within the CRD. One synonymous mutation, C(96)T, was

found to occur more frequently in all porcine disease groups investigated with the exception of

serositis, and in pigs diagnosed with E. coli, Mycoplasma spp., S. suis and PCV-2. Additional studies

are needed to determine the functional significance of this synonymous SNP and whether it may be

linked to other genetic mutations (Keirstead et al. 2011). Further genetic and disease association

studies will be required to fully understand the complex interactions between this class of lectins and

their detrimental effects on porcine health.

26

RETINOIC ACID-INDUCIBLE GENE-1-LIKE RECEPTORS

The retinoic acid-inducible genes (RIG)-1-like receptors (RLRs) are IFN-inducible

cytoplasmic RNA helicases. This recently discovered group of receptors plays a critical role in the

recognition of cytoplasmic RNA and DNA. The RLRs include retinoic acid-inducible gene 1 (RIG-1,

also known as DDX58), melanoma-differentiation-associated gene 5 (MDA-5 also known as

interferon-induced helicase/IFIH1 or helicard), RNA helicase LGP-2 (LGP-2 also known as DHX58),

DNA-dependent activator of IFN-regulatory factors (DAI also referred to as tumor stroma and

activated macrophage protein/DLM-1 or Z-DNA-binding protein 1/ZBP1), interferon-inducible

protein AIM-2 (absent in melanoma-2) and the more recently described ATP-dependent RNA

helicase DDX60 (DDX60) (Cui et al. 2008, Ha et al. 2008, Kato et al. 2006, Li et al. 2009, Miyashita

et al. 2011, Mogensen 2009, Moresco and Beutler 2010, Saito et al. 2007, Satoh et al. 2010, Schlee et

al. 2009, Takeuchi and Akira 2010, Wilkins and Gale 2010, Yoneyama et al. 2005). Table 1.4

summarizes the various ligands and cellular localization of the known retinoic acid-inducible gene

(RIG)-I–like receptors (RLRs).

These helicases contain an N-terminal caspase recruitment domain (CARD) (Mogensen 2009,

Takeuchi and Akira 2010, Wilkins and Gale 2010), a central DEAD box (DexD/H) helicase/ATPase

and a C-terminal regulatory domain; the CARD domain is absent in LGP-2 (Takeuchi and Akira

2010, Wilkins and Gale 2010, Yoneyama et al. 2005). The N-terminal CARDs of RIG-1 and MDA-5

trigger intracellular signaling pathways via the IFN-β promoter stimulator-1 (IPS-1 also known as

MAVS, VISA or CARDIF). IPS-1, is an adaptor molecule that possesses an N-terminal CARD

(Kawai et al. 2005) and promotes type 1-IFN production via tumour necrosis factor (TNF) receptor-

associated factor 3 (TRAF3) and TNF receptor type 1-associated DEATH domain protein (TRADD)

signaling pathways (Michallet et al. 2008) as well as IκB kinases (IKK-I and Tank binding

kinase1/TBK1) (Akira et al. 2006, Honda et al. 2006). Signaling via IκB kinases results in

phosphorylation of interferon-regulatory factor (IRF) 3 and IRF7 with subsequent transcription of

genes coding for type 1-IFN and IFN-inducible genes (Satoh et al. 2010). ATP is essential for type 1-

IFN production but the exact mechanism is still unknown. RIG-1, which may act as a translocase for

27

dsRNA, is postulated to change conformation and dimerize allowing catalyzation of ATP. The C-

terminal regulatory domain forms an RNA binding loop and is responsible for the binding of dsRNA

(Cui et al. 2008, Satoh et al. 2010, Takahasi et al. 2008, Takahasi et al. 2009, Takeuchi and Akira

2010, Wilkins and Gale 2010). The binding loop in MDA-5 is open and flat, and has low RNA

binding affinity whereas the binding loops of RIG-1 and LGP-2 are round and have a high RNA

binding avidity. RIG-1 ligands include short dsRNA and 5'- triphosphate dsRNA as found in RNA

and DNA viruses and activation of RIG-1 enhances type I-IFN signaling (Schlee et al. 2009, Schmidt

et al. 2009). The ligands for MDA-5, in turn, are longer dsRNA molecules and RNA with complex

folding and a higher order of structure (Pichlmair et al. 2009), such as the molecules found in RNA

viruses (esp. Picornaviridae) (Kato et al. 2006). LGP-2 has a higher binding affinity for dsRNA and

ssRNA than either RIG-1 or MDA-5. Binding occurs via the C-terminal domain which folds and

forms a basic RNA-binding groove that is bounded on one side by a critical RNA-binding loop

(Murali et al. 2008, Takahasi et al. 2009). Expression of LGP-2 is also induced in viral infections and

has been experimentally induced with poly I:C and LPS in pigs (Li et al. 2010). LGP-2 was originally

reported to function as a negative regulator of RIG-1 and MDA-5 by sequestering dsRNA or

inhibiting RIG-1 conformational changes (Rothenfusser et al. 2005, Saito et al. 2007, Yoneyama et al.

2005). Satoh et al. recently reported, however that LGP-2 has positive regulatory properties. These

investigators found that mice with a Lys to Ala (LGP2K30A/K30A

) mutation at position 30, have

impaired ATPase activity which, in turn, leads to impaired IFN-β responses. Similar results were also

observed in knock out (LGP2-/-

) mice and fibroblast cell lines (Satoh et al. 2010). It is proposed that

LGP-2 modifies RNA through its ATPase domain by removing RNA-binding proteins, altering the

conformation of RNA and/or modulating the intracellular localization of viral RNA. Since these

changes are associated with recognition by MDA-5 and RIG-1, LGP-2 is now believed to a positive

regulator of these receptors (Moresco and Beutler 2010, Satoh et al. 2010).

DAI and AIM-2 recognize dsDNA (Mogensen 2009, Schroder and Tschopp 2010, Wang et

al. 2008). DAI has three DNA binding domains, two for the left-handed Z-form of DNA (Z-DNA), Zα

and Zβ, and a third potential domain, the so-called D3 region. During signaling, DAI recruits TBK1

28

serine/threonine kinase and IRF3 resulting in downstream signaling and transcription of type 1-IFN,

similar to what is observed for RIG-1 and MDA-5 (Wang et al. 2008, Yanai et al. 2009). AIM-2 is a

343 amino acid protein with an N-terminal DAPIN/pyrin/PAAD domain (domain in apoptosis and

interferon response) which is represented by amino acids 1-87. AIM-2 also contains a C-terminal

HIN-200 protein domain, represented by amino acids 138 to 337. The HIN domain has two

oligonucleotide-binding folds (Fernandes-Alnemri et al. 2009), binds double stranded DNA (either

viral, bacterial, or even host) and acts as a cytosolic receptor for dsDNA. This leads to the

oligomerization of the inflammasome complex. The N-terminus of AIM2 interacts with the pyrin

domain of another protein, ASC (the apoptosis-associated speck-like protein containing a caspase

activation and recruitment domain). ASC also contains a CARD domain that recruits procaspase-1 to

the complex and leads to the auto activation of caspase-1, an enzyme that processes pro-inflammatory

cytokines (IL-1b and IL-18) (Schroder and Tschopp 2010).

Three non-synonymous coding SNPs, two of which have been linked to proposed structural

differences, have been reported in the porcine IFIH1 gene of oriental pig breeds (Meishan and

Jinhua); these SNPs were not identified in some western breeds (Landrace and Duroc) (Kojima-

Shibata et al. 2009). This same study also detected a total of 17 SNPs in the coding regions of the

DDX58 gene, including six non-synonymous SNPs, four of which are proposed to result in structural

differences. Functional assays on ligand recognition and SNP disease association studies are needed

to further investigate the significance of these identified SNPs. To date no promoter region

polymorphisms in the DDX58 gene have been identified in pigs. A single intronic polymorphism

(g.4919G>C), has been detected in the ninth intron of the porcine DHX58 gene (Li et al. 2010). An

association between the presence of this polymorphism and a variety of hematological parameters of 1

and 17 day old piglets was identified, including red cell distribution width as well as white blood cell

counts, absolute lymphocyte counts, and platelet distribution width respectively. Individuals with the

genotype CC or GC were also found to have significantly lower mean white blood cell counts than

individuals with the genotype GG. This may suggest a decreased ability of these individuals to

respond to infectious and inflammatory stimuli.

29

RIG-1-/-

and MDA5-/-

mice are highly susceptible to infection with various RNA viruses (Kato

et al. 2006). This suggests that the function of both RIG-1 and MDA-5 as essential PRRs is critical to

antiviral sensing. Genetic variations that may result in decreased production and/or function of these

non-redundant PRRs can have significant detrimental effects on host defences.

30

NUCLEOTIDE OLIGOMERIZATION DOMAIN-LIKE RECEPTORS

Nucleotide oligomerization domain (NOD)-like receptors (NLRs), previously known as

CATERPILLERs, NODs or NACHT–LRRs, play a key role as danger signals and intracellular

microbial sensors. NLRs consist of three distinct domains: a C-terminal leucine-rich repeat (LRR)

with structural homology to plant disease resistance proteins and TLRs, a central nucleotide-binding

domain (NACHT/NOD/NBD) and an N-terminal caspase activation and recruitment (CARD) or

pyrin (PYD) domain (Eisenbarth and Flavell 2009, Mogensen 2009, Schroder and Tschopp 2010,

Ting et al. 2008b, Williams et al. 2010). Twenty-two different receptors are currently classified as

NLRs. Based on phylogenetic analysis; NLRs can be divided into three distinct subfamilies that

include six nucleotide-binding oligomerization domain containing (NODs; including NOD1-2,

NOD3/NLRC3, NOD4/NLRC5, NOD5/NLRX1, and CIITA), 14 nucleotide-binding oligomerization

domain, leucine-rich repeat and pyrin domain containing (NLRPs/NALPs; including NLRP1-14) and

two ice protease-activating factor (IPAFs; including IPAF/NLRC4 and NAIP). All the NLRPs contain

a NACHT/NOD/NBD, PYD and LRR domain except for NLRP10 which has no LRR, the

significance of which is unclear (Schroder and Tschopp 2010). A second alternative classification

system has been proposed based on the N-terminal effector domain. Using this classification, NLRs

can be divided into four distinct groups: the NLRA [acidic transactivation domain], NLRB

[baculoviral inhibitory repeat (BIR)-like domain], NLRC [caspase recruitment domain (CARD)] and

NLRP [pyrin domain (PYD)] groups (Ting et al. 2008a). The C-terminal LRR domain serves as a

recognition receptor for PAMPs and DAMPs, especially for pathogens that have evaded cell surface

and endolysosomal mechanisms. (Eisenbarth and Flavell 2009, Schroder and Tschopp 2010, Williams

et al. 2010). ATP-dependent homotypic protein-protein oligomerization between NACHT domains of

NLRs (especially NLRP1,NLRP3/NALP3 and IPAF) results in the formation of high-molecular

weight complexes in the order of hexa- or heptamers (Eisenbarth and Flavell 2009, Martinon et al.

2002, Martinon et al. 2009, Schroder and Tschopp 2010, Williams et al. 2010). This complex then

recruits the CARD domain of adaptor protein ASC (apoptosis-associated speck-like protein) through

homotypic N-terminal CARD or the PYD domains interaction and in turn recruits the CARD domain

31

of multiple pro-caspase-1 proteins resulting in activation and forming the inflammasome. This

autocatalytic action of caspase-1, results in the secretion of pro-IL-1 , pro-IL18 and pro-IL-33 and the

formation of active compounds further stimulating the inflammatory cascade. Apart from the class II

trans-activator (CIITA) that acts as a key regulator of the expression of MHC class II genes (Steimle

et al. 2007, Steimle et al. 2007), all other NLRs are believed to act as intracellular PRRs. NOD1 and

NOD2, the most studied NLRs, recognize the breakdown products of bacterial cell walls (bacterial

peptidoglycans, meso-diaminopimelic acid and muramyl dipeptide, respectively) (Kufer et al. 2006,

Schroder and Tschopp 2010, Tohno et al. 2008a, Tohno et al. 2008b). NOD1 detects Gram-negative

bacteria as well as some Gram-positive bacteria, such as Bacillus and Listeria spp., while NOD2 acts

as a general sensor for both Gram-positive and Gram-negative bacteria (Kufer et al. 2006, Tohno et al.

2008a, Tohno et al. 2008b). The ligands and functions of NOD3 and NOD4 are unknown (Schroder

and Tschopp 2010). It has been proposed that NOD5/NLRX1, which is either located in the

mitochondrion or recruited to the outer mitochondrial membrane, suppresses signaling dependent

antiviral pathways and promotes generation of reactive oxygen species (ROS) (Arnoult et al. 2009,

Moore et al. 2008). The rest of the NLRs are poorly characterized but there is some evidence that

IPAF/NLRC4 is activated by flagellin and NLRP1b is induced by anthrax lethal toxin (Williams et al.

2010). The mechanisms involved in the formation and the function of inflammasomes are still a

subject of debate. NLRP3/NALP3, the best characterized inflammasome, can be induced by several

different compounds but the exact ligands are still largely unknown (Eisenbarth and Flavell 2009,

Martinon et al. 2002, Martinon et al. 2009, Schroder and Tschopp 2010, Williams et al. 2010).

Examples of NLR3P/NALP3 inducers include: Candida albicans and Saccharomyces cerevisiae

(Gross et al. 2009), bacterial pore-forming toxins (Listeria monocytogenes LLO toxin, Aeromonas

aerolysin and α-toxin produced by Staphylococcus aureus) (Schroder and Tschopp 2010), some

viruses (Kanneganti et al. 2006), insoluble crystals such as uric acid (Martinon et al. 2002, Martinon

et al. 2006), silica and asbestos (Cassel et al. 2008, Dostert et al. 2008), hyaluronan (Yamasaki et al.

2009), extracellular ATP (Mariathasan et al. 2006, Pelegrin and Surprenant 2006, Petrilli et al. 2007),

fibrillar amyloid-β peptide in Alzheimer’s disease brain plaques (Halle et al. 2008), released

lysosomal content and reactive oxygen species (Eisenbarth and Flavell 2009). Activation of the

32

inflammasome can also occur through PAMP or cytokine mediated activation of NF- B (Bauernfeind

et al. 2009) or via TNF-α and Il-1 (Franchi et al. 2009). The NLRs have also recently been shown to

induce pyroptosis, pyronecrosis (ASC-dependent but caspase-1-independent) and apoptosis (caspase-

1 and ASC dimerization dependent) (Eisenbarth and Flavell 2009, Ting et al. 2008b) as well as

initiation of the adaptive immune response, especially when activated by aluminum adjuvants, uric

acid and biodegradable polymer nanoparticles (Eisenbarth and Flavell 2009, Williams et al. 2010).

NLRX1 (NOD9) has been shown to inhibit IPS-1 signaling (Moore et al. 2008) and to be a

mitochondrial reactive oxygen species generator (Arnoult et al. 2009).

There are 22 known human NLR genes that have similar murine counterparts but these genes

have not been well characterized in swine (Schroder and Tschopp 2010). Fourteen non-synonymous

and thirty synonymous coding SNPs, distributed along the entire coding sequence, have been

identified in the porcine gene encoding NOD2 (NOD2) (Kojima-Shibata et al. 2009). Ten of the non-

synonymous SNPs have been linked to structural changes in the mature protein. Of these SNPs, the

T(1949)C polymorphism, located in the region encoding the hinge domain of the molecule, markedly

diminished the functional response of porcine NOD2 to muramyl dipeptide (MDP) when cloned into

expression vectors in a HEK293 human cell line. In contrast, the A(2197)C polymorphism, localized

in the region corresponding to the LRR, significantly enhanced the response of porcine NOD2 to this

ligand (Jozaki et al. 2009). The T(1949)C allele was found to be extremely rare among different pig

breeds (Landrace, Large White, Berkshire, Duroc, Hampshire, Meishan and Jinhua breeds) having

been detected in only a single individual of the Meishan breed and suggests that this mutation may

have a deleterious effect on the innate immune response (Jozaki et al. 2009). In contrast, the

A(2197)C allele was common in the commercial oriental (Meishan and Jinhua) and some western

(Duroc) breeds suggesting that this mutation may have a beneficial effect on innate immunity and

thus, prove useful as a genetic marker for disease resistance (Jozaki et al. 2009, Uenishi et al. 2012).

Confirmation of the potential effect of these SNPs will require in vivo disease association studies and

should also be extended to other pig populations from different geographic regions. Such studies,

especially those relating to human NLRs, are rapidly becoming an area of increased interest.

33

Mutations in NLRP1 have been associated with vitiligo in humans (Jin et al. 2007) and SNPs in

NLRP3 have been linked to increased pro-inflammatory signaling, food-induced anaphylaxis and

aspirin induced asthma (Hitomi et al. 2009). There are also reports that NLRP3 mutations that cause

an inherited gain in function can lead to auto-inflammatory disease (AID) and dysregulated

production of IL-1 (Williams et al. 2010). NLRP3 is activated in microglia by the fibrillar amyloid-

present within senile plaques of Alzheimer’s disease (Halle et al. 2008). Mutated CIITA has been

associated with hereditary MHC class II deficiency/bare lymphocyte syndrome (Steimle et al. 2007)

and a frame-shift mutation in the last LRR of NOD2 has been associated with Crohn’s disease and

Blau syndrome (Kufer et al. 2006, Schroder and Tschopp 2010). It is interesting to note that all of the

above-mentioned NLR-associated diseases in humans are primarily non-infectious in nature. This

may in part be due to the role NLRs play in the induction of inflammasome complexes as well as

apoptosis, pyronecrosis and pyroptosis. Little is known about the proteins in this group of PRRs and

their general interactions, ligands and responses remain unclear. As more information becomes

available it is likely that new disease associations may be identified.

34

ANTIMICROBIAL PEPTIDES

Antimicrobial peptides (AMPs) are a diverse and highly heterogeneous group of proteins that

have the ability to rapidly inactivate microbial organisms including Gram-positive and Gram-negative

bacteria as well as fungi and certain viruses (Zaiou and Gallo 2002). These peptides are widely

distributed, and are found in epithelial cells of mucosal surfaces (oral and gastrointestinal membranes)

and skin, as well as within the intracellular granules of leukocytes where they enhance antimicrobial

activity, particularly in granulocytes. All AMPs share two common structural characteristics, an

overall amphipathic topology and a net-positive charge at neutral pH due to a disproportionate

number of basic relative to acidic residues. The amphipathic topology allows AMPs to bind to, and

become inserted in, negatively charged surfaces such as microbial cell walls where they exert their

antimicrobial activity (Ganz et al. 1985, Ganz 2003, Tomasinsig and Zanetti 2005, Zanetti et al.

1995). Mammals have two major groups of AMPs: defensins (α and ) and cathelicidins (protegrins,

prophenins and myeloid antimicrobial peptides). Other mammalian antimicrobial peptides, which are

restricted to a few species only, include histatins (humans), dermcidin (humans), various anionic

peptides (sheep) and θ-defensins (primates) (Brogden et al. 1997, Ganz 2003, Linde et al. 2008). A

fourth, recently identified antimicrobial peptide is liver-expressed antimicrobial peptide LEAP-2 a

cysteine rich antimicrobial peptide (Hocquellet et al. 2010). Hepcidin (HAMP) was originally

identified in humans as an antimicrobial peptide produced in the liver and was subsequently named

liver-expressed antimicrobial peptide-1 (LEAP-1). Hepcidin is however best known for its role as an

iron-regulating protein and although it has recognised antimicrobial activity, its function as an innate

immune protein has not been extensively studied (Barthe et al. 2011, Hocquellet et al. 2012, Krause et

al. 2000, Park et al. 2001, Sang et al. 2006).

Alpha (α)- and beta ( )-defensins are polypeptides consisting of 90-100 amino acids. They

have a -sheet-rich folded core that is triple stranded and stabilized by a six-cysteine residue

framework containing three disulfide bonds. Defensins are differentiated from one another based on

the length of peptide segment between the six cysteine residues and the pattern of disulfide bond

formation (Ganz et al. 1985, Ganz 2003, Lehrer and Ganz 2002b, Selsted et al. 1985). They contain

35

clusters of positive/cationic charged amino acids (commonly arginine and lysine) which are

particularly abundant in defensins stored in granules containing negatively charged

glycosaminoglycans (Ganz 2003). The secondary and tertiary structure of defensins is highly variable

and depends on the exact amino acid sequence. Defensins are formed as a tripartite pre-pro-peptide

sequence with an amino-N-terminal sequence of approximately 19 amino acids, an anionic pro-piece

of approximately 45 amino acids that counterbalances the cationic carboxy-C-terminus, a region that

is approximately 30 amino acids in length and is important for the folding and/or prevention of

intracellular interactions with membranes (Ganz 2003, Lehrer and Ganz 2002b). More recently, θ-

defensins have been described. In contrast to α-and β-defensins, which are widely distributed across

species, θ-defensins are expressed only in the granulocytes of rhesus macaques and a few other

primates, including old world monkeys and orangutans (Linde et al. 2008). The genes encoding θ-

defensins, although present in humans, have acquired mutations that result in premature stop codons

and lack of expression. The θ-defensins are small double-stranded circular molecules (Ganz 2003,

Linde et al. 2008).

Cathelicidins, on the other hand, are a highly heterogeneous group of peptides that vary in

size (from 12 to 80 amino acid residues) and sequence configuration (Gennaro and Zanetti 2000,

Lehrer and Ganz 2002a, Linde et al. 2008, Tomasinsig and Zanetti 2005, Zanetti et al. 1995, Zanetti

2005). They contain a C-terminal cationic antimicrobial domain that is responsible for their

antimicrobial activity and an N-terminal cathelin terminus of approximately 100 residues that is

present on intracellular storage pro-forms of all cathelicidins (Lehrer and Ganz 2002a, Zaiou and

Gallo 2002, Zanetti et al. 1995, Zanetti 2005). The most common type of cathelicidins are linear

peptides that contain amphipathic α-helices (mimicking biological membranes) ranging from 23-40

amino acid residues in length. A second group of smaller cathelicidins, 12-18 amino acid residues in

length, contains -hairpin structures stabilized by one or two disulfide bonds. This region contains a

binding site for an elastase that cleaves primarily at valine, but also at alanine and isoleucine residues

in mammals (Shinnar et al. 2003). A third group of linear peptides (13 amino acid residues in length)

contains a high proportion of tryptophan residues and a fourth group (39-80 amino acid long),

36

contains repetitive proline motifs that form extended polyproline-type structures such as those found

in porcine PR-39, prophenins and bovine Bac (bactenecin) peptides (Tomasinsig and Zanetti 2005).

Defensins and cathelicidins are widely distributed in mammalian epithelial cells, phagocytes

(in primary/azurophil and secondary granules) and Paneth cells (Ganz 2003, Zanetti 2005). The

precise distribution varies considerably between species and individuals. For example, in contrast to

humans, no α-defensins are present in porcine granulocytes. However numerous cathelicidins are

found in the secondary granules of porcine granulocytes [e.g. protegrins 1-5(two-disulfide bridged),

prophenins 1 and 2 (linear and Pro rich), PR-39 (linear and Pro rich) and the porcine myeloid

antimicrobial peptides PMAP 23, 36 and 37 (α-helical AMPs)] (Kokryakov et al. 1993, Sang and

Blecha 2009, Tomasinsig and Zanetti 2005, Zaiou and Gallo 2002). -defensins (pBD-1 to 12) are

expressed at high levels in porcine tongue epithelium and at very low levels in all other porcine

epithelial surfaces (Kokryakov et al. 1993, Shi et al. 1999, Zhang et al. 1998). AMPs have a wide

range of activity against bacteria, fungi and viruses. The antimicrobial functions of AMPs are

activated by cleavage of the pro-sequence. The mechanism involves the folding of AMPs into

amphipathic structures, followed by permeabilization and insertion of the AMP into the target

membrane, a process that disrupts the membrane. AMPs also have chemotactic activity and there is

some evidence that they have direct antimicrobial killing properties (inhibition of bacterial DNA and

protein synthesis by PR-39) (Ganz 2003, Tomasinsig and Zanetti 2005, Zanetti 2005). Cathelicidins

are activated following cleavage of the pro-piece by proteases such as azurophilic elastase (myeloid

derived) and proteinase 3 present in neutrophils. Eventually, these proteases can also lead to the

degradation of cathelicidins. However, the arginine and proline rich cathelicidins are resistant to

protease degradation (Shinnar et al. 2003, Tomasinsig and Zanetti 2005).

The amino acid sequences of defensins and cathelicidins are highly variable across all species

(Ganz 2003, Zanetti 2005). The α- and -defensins of all species most likely evolved from a common

gene precursor (Liu et al. 1997). The cysteine framework of defensins and the cathelin domain of

cathelicidins are highly conserved across all species (Ganz 2003, Zanetti 2005). A study of ten

domestic cattle breeds, representing both Bos taurus and Bos indicus, indicated that the bovine gene

37

family encoding cathelicidins proteins (CATHL) is located on chromosome 22 (BTA22) of the Bos

taurus genome. Sixty SNPs, seven of which were non-synonymous, and five insertion-deletion

mutations were identified in the genes encoding for bovine cathelicidin-2, -5, -6, and -7 (Gillenwaters

et al. 2009). Additional investigation is needed to elucidate the effect that these CATHL gene

polymorphisms may exert on normal host defense and to identify potential disease resistance or

susceptibility conferring polymorphisms. No specific genetic defects or disease associations have

been reported in the antimicrobial peptide genes of swine.

38

PEPTIDOGLYCAN RECOGNITION PROTEINS

The peptidoglycan recognition proteins (PGRPs) are antimicrobial proteins originally

identified as innate immune proteins present in the hemolymph of insects (Yoshida et al. 1996). Four

mammalian homologues have been identified and based on their analogy with insect PGRPs, were

classified according to length as PGRP-S (short isoform), PGRP-L (long isoform), and PGRP-Iα and

PGRP-Iβ (intermediate isoforms) (Dziarski and Gupta 2010, Gottar et al. 2002, Kang et al. 1998, Liu

et al. 2001, Michel et al. 2001, Yoshida et al. 1996). The human proteins were subsequently renamed

and the new classification, PGLYRP-1 (for PGRP-S), PGLYRP-2 (for PGRP-L), PGLYRP-3 (for

PGRP-Iα) and PGLYRP-4 (for PGRP-Iβ), encoded for by the PGLYRP1, PGLYRP2, PGLYRP3 and

PGLYRP4 genes respectively, has become the official designation for all mammalian peptidoglycan

recognition proteins (PGLYRPs) (Dziarski and Gupta 2010). PGLYRPs contain one or more C-

terminal type 2 amidase domains referred to as the PGRP domain, which is approximately 165 amino

acids in length, as well as a signal peptide and an N-terminal domain (Liu et al. 2001, Royet and

Dziarski 2007). This PGRP amidase domain has structural similarities with bacteriophage and

bacterial type 2 amidases and contains three peripheral α-helices and several central β-sheet strands

which form a peptidoglycan-binding groove that is specific for muramyl-tripeptide (Guan et al. 2004,

Guan et al. 2005). A segment that is distinct from bacteriophage and bacterial type 2 amidases and

unique to PGLYRPs is present towards the N-terminus. This segment is often hydrophobic in nature

and perhaps plays a role in ligand binding (Dziarski and Gupta 2010). PGLYRP-1 and PGLYRP-2

each contain a single C-terminal PGRP domain while PGLYRP-3 and PGLYRP-4 contain two non-

identical PGRP domains (Dziarski and Gupta 2010, Royet and Dziarski 2007). The N-terminal

domain varies in length between the different PGLYRPs with that of PGLYRP-2 being approximately

twice the length of the other PGLYRPs. Within the center of the PGRP domains are two closely

spaced disulphide bonds formed between two conserved cysteine residues with a second disulfide

bond formed between two additional conserved cysteine residues. Another conserved pair of cysteine

residues is present within the middle of the PGRP domain forming a third disulphide bond in

PGLYRP-1 while the C-terminal PGRP domain of PGLYRP-3 and PGLYRP-4 also contains an

39

additional pair of cysteine residues forming a third disulfide bond (Royet and Dziarski 2007). These

bonds are essential for structural integrity and activity of the PGRP domain (Dziarski and Gupta 2010,

Guan et al. 2004, Royet and Dziarski 2007, Wang et al. 2003). Similar to the invertebrate amidase

PGRPs and bacteriophage type 2 amidases, PGLYRP-2 contains a conserved Zn2+

-binding site in the

peptidoglycan-binding groove, consisting of two histidine, one tyrosine, and one cysteine (named

C530 in human PGLYRP-2) (Wang et al. 2003). All mammalian PGLYRPs exist as secreted proteins

with PGLYRP-1, PGLYRP-3, and PGLYRP-4 forming disulfide-linked homodimers. When

expressed in the same cell, heterodimerization occurs between PGLYRP-3 and PGLYRP-4 (Dziarski

and Gupta 2010). Homodimerization of PGLYRP-2 is reported to occur independent of disulphide

bond formation (Dziarski and Gupta 2010).

PGLYRPs are expressed in a number of different tissues with some being restricted to very

specific locations. The mature PGLYRP-1 peptide is found in high quantities within tertiary granules

of polymorphonuclear granulocytes and PGLYRP1 is highly expressed in the same cell types in the

bone marrow (Dziarski and Gupta 2010, Kang et al. 1998, Liu et al. 2001, Tydell et al. 2006).

Additional sites of expression include the lactating mammary gland, intestinal M-cells as well as

epithelial cells and fibroblasts (Dziarski and Gupta 2010, Kappeler et al. 2004). The main site of

expression of PGLYRP2 is the liver with the mature protein circulating in the blood (Zhang et al.

2005). However, low levels of expression are also observed in the epithelium of the oral and intestinal

tract as well as fibroblasts and keratinocytes (Dziarski and Gupta 2010). Pigs contain two PGLYRP2

splice variants, a short and long variant. Like the PGLYRP2 gene of most other mammals, the long

isoform is predominantly expressed within the liver. The short form is expressed in a variety of tissues

including the bone marrow, intestine, liver, spleen, kidney, and the skin where it plays a role in

induction of expression of β–defensins (Li et al. 2006, Sang et al. 2005). The skin and mucosal

surfaces are the major sites of expression of PGLYRP3 and PGLYRP4 (Dziarski and Gupta 2010,

Royet and Dziarski 2007, Ueda et al. 2011). These proteins are excreted in various mucosal and

epidermal secretions including sweat, sebum, tears and mucus. The expression of PGLYRP3 and

40

PGLYRP4 can be increased through signaling of TLR2, TLR4, NOD1 and NOD2 (Saha et al. 2009,

Uehara et al. 2005).

As the name suggests, bacterial peptidoglycan (both the lysine and meso-diaminopimelic

acid-type) is the major ligand of PGLYRPs, which bind both Gram-positive and Gram-negative

bacteria (Cho et al. 2005, Dziarski and Gupta 2010, Dziarski et al. 2012, Kumar et al. 2005, Liu et al.

2001, Royet and Dziarski 2007). Binding affinity is determined by the third amino acid in the

peptidoglycan stem peptide and by the presence of N-acetyl-D-glucosamine and N-acetylmuramic

acid in the glycan backbone. At least three amino acids in the stem peptide are needed to attain high-

affinity binding (Cho et al. 2005, Guan et al. 2004). PGLYRPs are also capable of binding to

lipoteichoic acid, lipopolysaccharide and the 1, 3-β-d-glucan of fungi (Dziarski and Gupta 2010, Lee

et al. 2004). Adding a fourth amino acid to the peptide stem however, decreases binding affinity by

approximately 70-fold (Cho et al. 2005). PGLYRPs require divalent cations and N-glycosylation for

bactericidal activity. Although the mechanisms are largely unknown, it has been proposed that

PGLYRPs kill bacteria by inhibiting peptidoglycan synthesis (Dziarski and Gupta 2010). Human

PGLYRP1 is an important mediator in neutrophil-mediated killing of both intracellular and

extracellular bacteria (Cho et al. 2005). The antimicrobial effect of PGLYRPs is synergistic to that of

lysozyme and other granule associated antimicrobial peptides, and both lysozyme and PGLYRPs are

observed to colocalize in neutrophil extracellular traps (NETs), where they exert their bactericidal

effects (Cho et al. 2005). PGLYRP1 knockout mice (PGLYRP1-/-

) have an increased sensitivity to

intraperitoneal bacterial infection with low-pathogenic Gram-positive bacteria and are unable to kill

phagocytized bacteria (Dziarski et al. 2003).

A single non-synonymous SNP, C(419)A, has been reported in the human PGLYRP2 gene

(Dziarski and Gupta 2010, Wang et al. 2003). This SNP is located in the coding region of one of the

conserved cysteine residues and results in an amino acid change to alanine (Cys419Ala) and disrupts

amidase activity (Wang et al. 2003). Two synonymous coding region SNPs [G(102)C, G(480)A ] and

a single 3'UTR SNP [C(625)A], have been identified in the bovine PGLYRP1 gene. No SNPs have

been identified in the 1000 bp of the 5'-upstream promoter region (Pant et al. 2011). The G(480)A

41

synonymous SNP was found to be marginally associated with an increased risk of infection with

Mycobacterium avium subsp. paratuberculosis (Pant et al. 2011). It is important to note that the

G(480)A SNP is synonymous and does not change the amino acid residue at this position but does

change the amino acid codon. As shown for the human MDR1 gene, a shift to a rarer codon can result

in alterations of ribosome traffic and cotranslational folding, changes that may have an impact on

protein function (Kimchi-Sarfaty et al. 2007).

42

COMPLEMENT

The complement system consists of over 30 plasma proteins in addition to a number of cell

surface proteins. This system, which includes classical, alternative and lectin pathways, interacts with

host molecules to exert its effects on both the innate and adaptive immune systems. Although often

depicted as involving simple linear pathways, the various complement cascades form a tight network

of interwoven reactions (Ricklin et al. 2010, Walport 2001) that lead, ultimately, to the activation of

C3 and the formation of a terminal membrane attack complex (MAC). Following an interaction

between C5b, C6 and C7, the MAC complex inserts itself into the microbial membrane where it binds

C8 and C9 and promotes membrane disruption and cell lysis. The various factors were named

according to their historical discovery and do not necessarily follow the order of events in the cascade.

The classic pathway is antibody dependent and involves factors C1 through C9. C1q, a PRR that

recognizes microbial organisms, apoptotic cells and endogenous danger signals can activate the

complement cascade, either through direct pathogen or ligand binding or through interaction with the

Fc portion of antigen bound antibodies (immune complexes). This involves the formation of the C1

complex and the activation of associated C1r and C1s proteases. The C1 complex then cleaves C4 into

C4a and C4b followed by C4b deposition onto the surface of the inciting target, a process that results

in opsonisation. C4b binds to C2 and cleaves it into C2a and C2b generating the C3 convertase

(C4b2b). This, in turn, cleaves C3 resulting in amplification of down-stream effector functions

(Wallport 2001, Ricklin 2010). Both the C4a and C3a fragments act as a potent pro-inflammatory and

chemotactic anaphylatoxins. The lectin pathway (often referred to as the mannan-binding lectin

pathway) is activated by MBLs and FCNs (Endo et al. 2006, Fujita et al. 2004a, Fujita et al. 2004b,

Girija et al. 2007, Rossi et al. 2001, Schwaeble et al. 2002, Walport 2001) in association with the

MBL associated serine proteases (MASPs) and sMAP (a truncated form of MASP-2). MASP-2

cleaves both C4 and C2 forming the same C3 convertase enzyme complex as seen in the classic

pathway. MASP-1 cleaves C2 only, acting as a supplementing system to increase the efficiency of C3

convertase formation (Chen and Wallis 2004, Dobo et al. 2009, Rawal et al. 2008). Interactions

between MBL and MASP/sMAP take place through the MASP binding motif, GEKGEP, a six amino

acid sequence in the collagen-like domain of MBL and in the Clr/Cls/Uegf/bone morphogenetic

43

protein 1 (CUB) and the epidermal growth factor-like (EGF-like) domains of MASP/sMAP (Feinberg

et al. 2003, Teillet et al. 2008, Wallis et al. 2004). A similar mechanism is proposed for FCN

(Gregory et al. 2004, Ichijo et al. 1993, Teillet et al. 2008). sMAP is proposed to play a regulatory role

in lectin-mediated complement activation by competing with MASP-2 binding to MBL and FCN

(Endo et al. 2007).

The alternative pathway is activated by protein, lipid and carbohydrate structures present on

the microbial surface as well as by spontaneous low-grade hydrolysis of a thioester bond in C3

(Harboe and Mollnes 2008, Walport 2001). After cleavage, the exposed highly reactive thioester

group on C3b forms a covalent bond with a nearby target membrane, creating an amplification loop.

C3b can also bind directly to C3 convertase to form C5 convertase. C3b then binds factor B, a C2

homologous protein, and forms the C3bB complex which is subsequently cleaved by factor D,

resulting in formation of an alternative pathway C3 convertase complex (C3bBb). This complex then

cleaves C3 into C3a and C3b, a process that leads to opsonisation of the target membrane. In both the

classical and alternative complement pathways, some C3b binds to C4b to form the C5 convertase

enzyme (Walport 2001). The alternative pathway can also be directly activated by properdin (or factor

P), a gamma globulin released by activated neutrophils. Properdin also enhances the alternative

pathway by stabilizing the C3bBb complex (Kemper et al. 2010, Spitzer et al. 2007). The cleavage of

C5 results in the formation of C5a and C5b. C5a acts as a potent pro-inflammatory and chemotactic

anaphylatoxin while C5b recruits the remaining components (C5b to C9) needed to form the terminal

MAC complex.

C3, a central factor of all complement cascades, has been intensely investigated. Sequencing

and SNP evaluation has revealed that the C3 genes are relatively well conserved across mammalian

species with the porcine gene being the most homologous to human C3 (Wimmers et al. 2003). Two

of the best known polymorphisms in humans, a C(364)G SNP and a second polymorphism defined by

the monoclonal antibody HAV 4-1 have been linked to several infectious and autoimmune diseases

(Botto et al. 1990). The C(364)G non-synonymous SNP is located in exon 3 and results in an arginine

to glycine amino acid substitution with two associated allotypic forms: C3S and C3F. The HAV 4-1

44

polymorphism results in a proline to leucine substitution and is located at position 292 in exon 9 in the

region that encodes for the β-chain of C3. The porcine C3 gene encodes for a 1661 amino acid C3

precursor protein and is comprised of 41 exons and 40 introns. The C3 gene in turn is flanked by a

444 base pair promoter and an 881 base pair 3'-UTR region. The precursor protein consists of a 22

amino acid signaling protein, a 643 amino acid β-chain (including a conserved sequence of the α2-

macroglobulin family N-terminal region) and a 992 amino acid α chain (including a conserved

sequence that is similar to the C-terminus and anaphylatoxin domains of the α2-macroglobulin

family). The α- and β-chains of porcine C3 are connected by a short peptide, RKRR, which is present

within the pre-proprotein at amino acid position 666 to 669 (Wimmers et al. 2003). An internal

thioester bond (GCGEQ), located between amino acids 1007 and 1011, has been shown to play an

important role in the binding of molecules on foreign surfaces (de Bruijn and Fey 1985). Another

thioester at amino acid 1124 serves as the thioester-associated catalytic histidine. A conserved

sequence containing several cysteine disulfide bonds, distributed across the surface of the C3

molecule, connects the various C3 fragments. Similar to the porcine C3 gene, the porcine C5 gene

(C5) is highly homologous (78 %) to that of the human C5 gene and also shows high homology to

other mammalian sequences (73 % mouse and 71 % rat) (Kumar et al. 2004). The complete C5 cDNA

sequence is 5422 nucleotides in length and ends in a polyA tail. The polyadenylation signal

(ATTAAA) is similarly located to the human analog between nucleotides 5400 and 5405. The

predicted protein sequence is 1677 amino acids in length and only one amino acid longer than its

human counterpart. The signal peptide is formed by the first 18 amino acids followed by a 655 amino

acid β-chain (including a conserved sequence of the α2-macroglobulin family N-terminal region from

amino acids 19 to 631) and a 1000 amino acid α chain (including an anaphylatoxin-like domain from

amino acids 698 to 732; a conserved α2-macroglobulin family C-terminal region from amino acids

758 to 1509 and a NTR/C345C module from amino acids 1549 to 1659) (Kumar et al. 2004).

Five SNPs have been identified in the gene encoding the porcine C3 molecule (C3), one each

within the 5'UTR (C(20)T), intron 13 (T(204)C), exon 15 (C(1905)A), exon 30 (G(3882)A) and the

3'UTR (poly dT) (Wimmers et al. 2001, Wimmers et al. 2003). Collectively, these SNPs were shown

45

to be associated with decreased C3 mRNA expression in a single research population (Wimmers et al.

2003). The functional mechanisms and contribution of each individual SNP to alterations in

expression remains to be determined. Studies should also be expanded to include additional

populations to further evaluate the effect of these SNPs on constitutive expression of C3. Furthermore

it is also important to further evaluate the exact consequence that decreased C3 expression has on the

complement cascade as a whole. Four synonymous SNPs have been identified in the porcine C5 gene;

one transversion [A(1044)C] and three transition SNPs [A(1203)G; T(2766)C and A(3018)G] (Kumar

et al. 2004). Significant variations in the classical and alternative complement activities as well as

serum haptoglobin and C3c protein levels were identified between some of the segregating SNP

genotypes for the A(1044)C SNP but not the other SNPs. Classical complement activity in pigs

homozygous AA for the A(1044)C SNP were found to have 7.35 and 9.6 units higher activity (p <

0.05) than the AC and CC genotypes, respectively. In contrast the alternative complement activity of

homozygous AA individuals was 5.35 and 4.25 units lower (p < 0.05) than the AC and CC genotype

respectively. The effect on C3c and haptoglobin serum concentrations was less prominent. In pigs

homozygous CC, the C3c protein levels were 0.014 and 0.009 of a unit higher in concentration than

the AA and AC genotypes, respectively while serum haptoglobin levels were 0.123 and 0.088 of a

unit higher (p < 0.05) than the AA and AC genotypes respectively. In this case it is unclear how this

synonymous SNP alters protein function and further investigation is necessary to elucidate the

significance of this SNP in innate immune defences. Factor H deficiency has also been described in

the Norwegian Yorkshire breed and is associated with the development of lethal

membranoproliferative glomerulonephritis (Jansen et al. 1995). This deficiency is transmitted as a

simple autosomal recessive trait with full penetrance however the underlying genetic defect has not

been identified. Factor H deficiency historically has been limited to the Norwegian Yorkshire

population and has largely been eliminated in this country through an enzyme immunoassay test to

remove putative carriers from the breeding line (Hogasen et al. 1997).

In humans, several different complement factor deficiencies are associated with acute and

severe infections (Wallis et al. 2010). Defective clearance of immune complexes with subsequent

46

glomerulonephritis (Botto et al. 1998, Walport 2001) and an increased risk for the development of

autoimmune diseases such as systemic lupus erythematosus (Lewis and Botto 2006, Lu et al. 2008)

have been reported. In Alzheimer’s disease, C1q binds to normal, non-infectious prion proteins and

activates the complement cascade (Sim et al. 2007), augmenting disease progression (Yasojima et al.

1999). Complement activation has also been implicated in the pathogenesis of reperfusion injury (e.g.

myocardial infarcts and kidney disease) (Mollnes et al. 2002, Wallis et al. 2010). Deficiencies in C3

have been associated with an increased incidence of pyogenic bacterial infections,

membranoproliferative glomerulonephritis and Neisserial infections in humans. C1 deficiency has

been associated with angioedema. C1q, C1r and C1s, C4 and C2 deficiencies have all been associated

with systemic lupus erythematosus while factor H and I deficiencies can lead to hemolytic uremic

syndrome as well as membranoproliferative glomerulonephritis (Walport 2001).

GENETIC POLYMORPHISM AND THE INNATE IMMUNE GENOME

Although there are many differences in the structure, intra- or extracellular location and down-stream

signalling pathways between the various classes of secreted, membrane-bound and intracellular

proteins and receptors of the innate immune system, they ultimately share a common goal, one that is

rooted in the detection and elimination of invading pathogens. Alteration in the normal and essential

functioning of this critical defense component such as those resulting from underlying genetic

variation can have a significant impact on the ability of an individual to resist and clear infectious

pathogens. Despite the critical role that these molecules play, studies aimed at investigating the

relationship between genetic variations in innate immune proteins and resistance to infectious disease

are limited. In humans, a few single nucleotide polymorphisms (SNPs) and other genetic variations in

some innate response receptors have been shown to alter the structure and functional levels of PRRs

and their effect on disease resistance has been extensively studied (Garred et al. 2006, Lahti et al.

2002, Leth-Larsen et al. 2005, Madsen et al. 1994, Pothlichet et al. 2009, Rallabhandi et al. 2006,

Wallis et al. 2010, Wang et al. 2003). In domestic animals the identification of disease conferring

genetic polymorphisms (such as SNPs, insertions, deletions and other genetic variations) are also

47

becoming increasingly important. These genetic variations represent important targets (markers) that

could be used in selective breeding strategies (Ibeagha-Awemu et al. 2008). In pigs, only a small

number of the studies have focussed on such genetic defects within the genes composing the innate

immune system and like in humans some of these genetic polymorphisms have been shown to have a

detrimental effect on porcine host resistance to infectious disease (Bergman et al. 2012, Jozaki et al.

2009, Juul-Madsen et al. 2006, Juul-Madsen et al. 2011, Keirstead et al. 2011, Kojima-Shibata et al.

2009, Lillie et al. 2006, Lillie et al. 2007, Palermo et al. 2009, Phatsara et al. 2007, Shinkai et al.

2012, Uenishi and Shinkai 2009, Uenishi et al. 2011, Uenishi et al. 2012). Additional information on

the function and interactions of the various porcine innate immune proteins should enhance our

understanding of innate disease resistance in pigs. Of specific interest is the identification of

additional genetic variations that may underlie abnormalities within these important factors. The

identification of such genetic variations are likely to serve as important disease resistance markers that

can be included in future genetic strategies aimed at improving innate disease resistance of swine.

48

Table 1.1. Ligand and cellular localization of the Toll-like receptors.

Toll-Like receptor Gene Symbol Ligand Cellular location

TLR1 TLR1 Triacyl-lipoprotein (bacteria,

viruses)

Cell membrane

TLR2 TLR2 Lipoprotein (bacteria, viruses,

parasites)

Cell membrane

TLR3 TLR3 dsRNA (viruses) Endolysosomal

TLR4 TLR4 Lipopolysaccharide Cell membrane

TLR5 TLR5 Flagellin (flagellated bacteria) Cell membrane

TLR6 TLR6 Diacyl-lipoprotein (bacteria,

viruses)

Cell membrane

TLR7

(human TLR8)

TLR7

(TLR8)

ssRNA (viruses, bacteria) and

purine analogs

(imidazoquinolone)

Endolysosomal

TLR9 TLR9 CpG DNA (viruses, bacteria,

protozoa)

Endolysosomal

TLR10 TLR10 Unknown Endolysosomal

TLR11 TLR11 Profilin (protozoa) Cell membrane

49

Table 1.2. Sugar specificity and species distribution of various collagenous lectins.

Table adapted from Lillie et al. (Lillie et al. 2005).

Collagenous lectin Gene symbol Sugar ligand Species

MBL-A MBL1 ManNAc, GlcNAc, Man,

Glc

Swine, cattle, horses, horses,

mouse, rat and primates

(MBL1P pseudo gene in

humans and chimpanzees)

MBL-C MBL2 ManNAc, GlcNAc, Man,

Fuc, Glc, Mal, Gal, Lac,

GalNAc

Swine, cattle, horses,

mouse, rat, human and other

primates

SP-A SFTPA1 ManNAc, Fuc, Mal, Glc,

Man

Swine, cattle, horses, sheep,

dog, rat, mouse, human and

other primates

SP-D SFTPD Mal, Man, Gal, GlcNAc,

Glc, Fuc

Swine, cattle, horse, sheep,

dog, rat, mouse, rabbit,

humans and other primates

Conglutinin CGN1 GlcNAc, Fuc, Man, Glc,

ManNAc, Mal

Cattle

CL-43 CL43 Man, ManNAc, Fuc,

GlcNAc, Glc

Cattle

CL-46 CL46 GlcNAc, ManNAc, Man,

Mal, Glc, Gal, Lac,

GalNAc

Cattle

CL-L1 COLEC10 Man, Gal, Fuc, GlcNAc Human and mouse

CL-P1 COLEC12 Not known Human, other primates and

mouse

Ficolin-α FCN1 GlcNAc Swine

Ficolin-β FCN2 GlcNAc Swine, Cattle

M-ficolin FCN1 GlcNAc Human, other primates

L-ficolin FCN2 GlcNAc Human, other primates

H-ficolin FCN3 GlcNAc, Fuc, GalNAc Human, other primates

(pseudo gene in rodents)

Ficolin-A FCNA GlcNAc Mouse, rat

Ficolin-B FCNB Not known Mouse, rat

50

Table 1.3. Ligand and cellular localization of the C-type lectin receptors and scavenger

receptors.

Receptor Gene symbol Ligand Cellular location

Dectin-1, -2, -3 CLEC7A

CLEC6A

β1,3 and β1,6 linked glucans

(fungi, plants and bacteria)

Cell membrane

(myeloid cells)

MINCLE CLEC4E SAP130

(fungi, self)

Cell membrane

MARCO MARCO Various

(bacteria, viruses)

Cell membrane

(pulmonary

macrophages)

DC-SIGN CD209 Various

(bacteria, viruses)

Cell membrane

(dendritic cells)

51

Table 1.4. Ligand and cellular localization of the retinoic acid-inducible gene-I–like receptors.

RLR Gene symbol Ligand Cellular location

RIG-1 DDX58 Short and 5' triphosphate dsRNA

(RNA and DNA viruses)

Cytoplasmic

MDA-5 IFIH1 Longer dsRNA molecules and

higher order structure RNA (RNA

viruses)

Cytoplasmic

LGP-2 DHX58 dsRNA and ssRNA Cytoplasmic

DAI ZBP1 dsDNA Cytoplasmic

AIM2 AIM2 dsDNA (viral, bacterial and self) Cytoplasmic

52

Table 1.5. Ligand and cellular localization of the peptidoglycan recognition proteins.

PGLYRP Gene symbol Ligand Tissue distribution Mechanism of action

PGLYRP-1

(PGRP-S)

PGLYRP1 Bacterial

peptidoglycan

Tertiary granules of

granulocytes

Bactericidal

PGLYRP-2

(PGRP-L)

PGLYRP2 Bacterial

peptidoglycan

Liver and epithelia Bactericidal

N-acetylmuramoyl-L-

alanine amidase

PGLYRP-3

(PGRP-Iα)

PGLYRP3 Bacterial

peptidoglycan

Skin, mucous

membranes,

secretions (saliva,

sweat, sebum)

Bactericidal

PGLYRP-4

(PGRP-Iβ)

PGLYRP4 Bacterial

peptidoglycan

Skin, mucous

membranes,

secretions (saliva,

sweat, sebum)

Bactericidal

53

CHAPTER 2: CONSTITUTIVE VARIATION IN THE HEPATIC INNATE IMMUNE

TRANSCRIPTOME OF HEALTHY PIGS

This chapter corresponds to a manuscript of the same title to be submitted with the following

authorship:

Snyman HN, Hammermueller JD, Hayes MA, Lillie BN (2013)

ABSTRACT

The detrimental effects of infectious diseases still pose one of the most significant hurdles

plaguing the global swine industry today. Although this is a multifactorial problem involving a variety

of host, environment and pathogen interactions; early intervention by the host innate immune system

is a critical component in the host defense to infectious diseases. Emerging evidence also suggests

that alterations in the expression of some innate immune genes can have a detrimental effect on the

susceptibility of swine to common infectious diseases. Some of this observed variation can be

explained by specific genetic polymorphisms that alter transcriptional regulation and a number of

single nucleotide polymorphisms (SNPs) in the innate immune genes of swine have been shown to be

associated with decreased (or enhanced) gene expression. Most studies aimed at identifying genetic

variation in pigs have involved a targeted single gene approach. In this study, we used a porcine

specific microarray (Agilent® Porcine Gene Expression Microarray) to quantify constitutive hepatic

expression of a 114 innate immune genes in 96 healthy market weight pigs. Constitutive variation was

determined by comparing the mean gene expression values of the highest and lowest expressing pigs

for each gene. Using this approach, we identified 30 innate immune genes with widely variable gene

expression. Among these were DDX3Y, MBL2, SCGB1A1, PR39, PMAP-23, PMAP-37, NPG4,

SFTPD, PGLYRP1 and HAMP. Some of the high variability in constitutive expression of these

resistance-associated proteins and pattern recognition receptor genes might result from genetic

differences (SNPs, insertions, deletions or other genetic variations), some of which are predicted to

impact resistance of pigs to infectious diseases.

54

INTRODUCTION

Among the major limiting factors resulting in significant strain on the production, growth

performance and economics of the global swine industry today, are the many infectious agents and

disease syndromes that commonly affect commercial swine populations. These are typically

multifactorial problems with complex interactions among pathogen, environmental, and host genetic

factors. Infectious disease syndromes that commonly affect pigs are often caused by multiple co-

infecting bacterial and viral pathogens which further complicate this problem. A critical component of

the complex host defense system is the ancient and evolutionarily conserved innate immune system

which is composed of an elaborate network of secreted, membrane-bound and intracellular proteins

that have the ability, either individually or collectively, to detect and destroy invading pathogens

(Medzhitov 2009, Mogensen 2009). Unlike the adaptive immune system in which genetic diversity

can be acquired by recombination and clonal selection of lymphocytes in an individual, functional

changes in innate immune genes evolves via germ line mutations and selection (Janeway 1989,

Medzhitov 2009).

As in humans, emerging evidence suggests that polymorphisms in the pig genome, including

those that alter the expression of innate immune genes, can have a detrimental effect on the incidence

and susceptibility of these animals to common, economically important infectious diseases (Garred et

al. 2003, Garred and Madsen 2004, Ibeagha-Awemu et al. 2008, Jozaki et al. 2009, Juul-Madsen et al.

2011, Keirstead et al. 2011, Lillie et al. 2006, Lillie et al. 2007, Madsen et al. 1998, Uenishi et al.

2011, Uenishi et al. 2012). The innate immune response to infectious diseases is, in itself, a complex

multifactorial process, involving a large number of interacting factors and pathways, as well as a large

cushion of redundancy. The opportunity exists to characterise the innate immune response and disease

resistance phenotypes at a more complex genetic level.

To date, most studies aimed at identifying variation in gene expression of innate immune

proteins in swine have been limited to a targeted single gene approach. These studies have been

particularly focussed on a limited number of target proteins with the result that many innate immune

genes remain to be investigated. Advances in high throughput sequencing and whole genome

microarray analysis are revolutionizing the medical and biological sciences and there is a growing

55

interest in applying these technologies to the porcine genome (Tuggle et al. 2007). Combining these

technological advances along with the sequencing of the porcine genome and continued improvement

of gene annotation now make it possible to expand these studies to a more complex genomic level.

The majority of porcine microarray studies have focussed on genes that are differentially

expressed following experimental or natural infection with a limited number of pathogens (Bao et al.

2012, Fernandes et al. 2012, Gladue et al. 2010, Hedegaard et al. 2007, Lee et al. 2010, Li et al. 2010,

Ma et al. 2012, Mortensen et al. 2011, Moser et al. 2004, Moser et al. 2008, Sanz-Santos et al. 2011,

Skovgaard et al. 2010, Tomas et al. 2010, Wysocki et al. 2012) and few studies have aimed at

evaluating gene expression at a normal constitutive level (Freeman et al. 2012). The interpretation of

altered gene expression in infection studies can also be complicated by degenerative and

inflammatory changes resulting from tissue destruction. The liver is a major source of circulating

innate immune proteins and also contains large numbers of monocyte/macrophages, Kupffer cells and

NK cells that play a central role in the identification and elimination of pathogens (Exley and Koziel

2004). Since the liver is such a central innate immune organ, and anatomically and physiologically

more consistent in composition than respiratory or gastroenteric tissues, it provides an accessible way

to explore genetic differences in expression of a large number of genes of the innate immune and

many other physiological systems. In this study, we used porcine-specific expression microarray

technology to evaluate the constitutive hepatic expression of innate immune genes in healthy market

weight pigs. Using this approach we identified many genes that exhibited major alterations in

constitutive gene expression. This study expands the knowledge of the hepatic immune transcriptome

and paves the way for additional studies to identify genetic mutations (SNPs, insertions, deletions)

responsible for these alterations in the innate immune system.

56

MATERIALS AND METHODS

Sample Acquisition

Liver samples of healthy market weight pigs were collected at the time of slaughter from a

large southern Ontario pig processing facility. All of the animals were considered to be terminally

crossed commercial pigs of unspecified breeds. A total of 1003 liver samples were collected from pigs

with unique production unit tattoo numbers. A median of 6 samples (range 1 to 21) were collected

from each of 158 different production units. A portion of each liver sample was frozen and stored at -

80 ºC in a 2 mL microcentrifuge tube until required for DNA extraction. Additional portions were

placed in RNAlater for subsequent RNA extraction (two 30 mg samples in each of two 2 mL

microcentrifuge tubes, each of which contained 600 L of RNAlater) (Ambion, Austin TX, USA).

According to the manufacturer’s protocol and published recommendations, these samples were kept

on ice and then placed at 4 ºC for 24 h, followed by 24 h at -20 ºC and storage at -80 ºC (Kasahara et

al. 2006).

DNA and RNA Extraction

Total DNA was extracted from all 1003 liver samples using the QIAGEN DNeasy® tissue kit

(QIAGEN Inc., Mississauga, ON) according to the manufacturer’s protocol. Total RNA was extracted

from the RNAlater stabilized liver samples using the QIAGEN RNeasy minikit® and QIAzol tissue

lysis reagent according to the manufacturer’s protocol. Liver samples were homogenized using a Bio-

Gen PRO200 Homogenizer (Diamed Lab Supplies, Inc., Mississauga, ON). The yield/concentration

of purified DNA and RNA was determined spectrophotometrically using the Nanodrop® (Thermo

Fisher Scientific, Wilmington, DE) and Nanovue® (GE Healthcare, Baie d’Urfe, QC)

spectrophotometer systems at a wavelength of 260 nm. DNA and RNA purity was determined by

measuring the absorbance ratio at 280 and 260 nm. The quality of the RNA was further assessed by

calculating an RNA Integrity Number (RIN) using the Bioanalyzer® system (Agilent Technologies

Canada Inc., Mississauga, ON) at the Advanced Analysis Centre (AAC) Genomics Facility

57

(University of Guelph, Science Complex, Guelph, ON). Only RNA samples with a RIN number of >

7 were selected for microarray expression studies (Madabusi et al. 2006, Schroeder et al. 2006,

Thompson et al. 2007). All purified nucleic acid samples were stored at -80 ºC.

SNP Genotyping

To aid in the selection of a genetically diverse population of pigs for microarray expression

analysis, all pigs were genotyped for 21 previously identified innate immune response gene SNPs

(Keirstead et al. 2011, Lillie et al. 2006) (Appendix I). Aliquots (15 – 45 ng/ μL) of DNA were placed

in a 96-well plates and submitted to the UHN Clinical Genomics Centre at the Mount Sinai Hospital,

Toronto, Ontario for genotyping using Sequenom MassARRAY® matrix-assisted laser

desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (Sequenom, San Diego, CA,

USA). A subset of 96 pigs was selected for microarray expression analysis based on the genetic

heterogeneity of six of these innate immune gene SNPs, five of which were located in promoter

regions (Table 2.1). The selection of these SNPs was based on their promoter location and previously

identified associations with variation in constitutive gene expression and/or documented disease

associations for some of these SNPs (Keirstead et al. 2011, Lillie et al. 2007). Each pig’s tattoo

number was recorded at the time of collection and this number was used to identify the production

unit origin of each pig in this study. A total of 38 unique SNP combination haplotypes and 68 out of

the total 158 unique production unit tattoo numbers were represented in this subset of pigs subjected

to microarray analysis. A median of 2 (range 1 to 7) pigs were tested for each of the 38 SNP

haplotypes and at least one pig was tested from the 68 different production units (range 1 to 4).

Whole Genome Microarray Analysis

Microarray analysis was performed at the University Health Network (UHN) Microarray

Centre (Toronto, Ontario) using the 4 x 44K Agilent® Porcine Gene Expression Microarray chip

platform (Agilent Technologies Canada Inc., Mississauga, ON) containing 43,603 oligomer probes.

The raw microarray expression data for each probe was median normalized, log2-transformed and

analyzed using arrayQualityMetrics software (UHN, Toronto, ON). Outliers, weak and failed arrays

58

(speckling and blocking issues) were discarded from further analysis (n = 8) as well as two additional

outliers identified at the time of unsupervised hierarchical agglomerative clustering; resulting in a

total of 86 pigs with 38 different SNP genotypes (median of 2; range 1 to 5) from 64 different

production units.

Constitutive variation in gene expression was defined as the gene expression ratio (GER)

(log2) of the mean gene expression of the top 50 % (n = 43) compared to the mean gene expression of

the bottom 6 % (n = 5) of pigs. Variable expression was then ranked based on the calculated GER for

each gene (Table 2.5). For comparative purposes, we also calculated GERs for the top 50 % vs. the

bottom 10 % (n = 9) and bottom 50 % of pigs; the top 20 % (n = 17) vs. the bottom 20 % (n = 17),

top 10 % (n = 9) and bottom 10 % (n = 9) of pigs; and the top 6 % (n = 5) of pigs vs. the bottom 50 %

(n = 43) (Appendix II). Different calculated GER sets were then compared to each other and an

average rank was calculated (Appendix III).When available; probe ontologies, gene symbols and/or

gene descriptions were used to identify microarray probes linked to genes with known or putative

innate immune function. For probes with unknown annotation or gene ontologies, the nucleotide

sequence of the probe was used for identification in conjunction (when available) with the associated

EnsemblID, GenBank-, Primary- or RefSeq accession number, TIGRID or UniGeneID and with

mRNA sequence data from the NCBI GenBank (http://www.ncbi.nlm.nih.gov/gene) and/or the

Ensembl online genome browser database (Flicek et al. 2013).

dCHIP software (http://www.hsph.harvard.edu/cli/complab/dchip/) was used for unsupervised

hierarchical agglomerative clustering of the 114 identified innate immune genes using average linkage

as clustering technique and the Euclidean metric as a distance metric (Eisen et al. 1998). Some genes

contained duplicate or multiple probes. Duplicate and multiple probes that clustered together and

exhibited similar expression patterns on clustering analysis were then combined by calculating an

average normalized expression value for each pig and the clustering analysis was repeated to generate

a final microarray expression heat map (Figure 2.1).

59

Sex-Genotyping

The sex of the pigs used in the microarray expression study (n = 88) was determined using a duplex

PCR assay that amplified a 198 bp fragment of the coding region of the Y-encoded, testis-specific

protein (TSPY) in addition to a 466 bp sequence of the coding region of the mitochondrial cytochrome

b (MT-CYB) (amplified as a positive control) (Irwin et al. 1991). The primers used for the TSPY and

MT-CYB amplifications are listed in Table 2.2. PCR reactions were performed on a Lightcycler® 480

system (Roche Applied Science, Salt Lake City, Utah) according to the manufacturer’s

recommendations (10 µl reaction volume) with primers at a final concentrations of 0.5 µM. PCR

parameters were as follows: pre-incubation at 95 ºC for 5 min, followed by 30 cycles of denaturation

at 95 ºC for 10 s, annealing at 60 ºC for 10 s, and elongation at 72 ºC for 40 s. Melting curve analysis

was used to determine whether the sample contained both the TSPY and MT-CYB genes (male) or

only the MT-CYB gene (female), with results confirmed by visualization of the product by agarose gel

electrophoresis (2 % gel run in 0.5 X TBE buffer and stained with SYBR SAFE) (data not shown).

The fluorescence threshold and amplified product melting temperature were calculated using

Lightcycler® 480 system software (Figure 2.3). DNA sequencing confirmed the amplified products

were TSPY and MT-CYB.

60

Table 2.1. List of previously identified innate immune response gene SNPs used for microarray expression selection.

Innate immune factor Gene Symbol SNP ID

Ficolin-β FCN2 FCN2 g.-134A>G

Mannan-binding lectin-C MBL2 MBL2 g.-2158T>C

Mannan-binding lectin-C MBL2 MBL2 g.-1646G>T

Mannan-binding lectin-C MBL2 MBL2 g.-1091G>A

Mannan-binding lectin-C MBL2 MBL2 g.-261C>T

Toll-like receptor 4 TLR4 TLR4 c.962G>A

SNP nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000)

Table 2.2. Primers used for PCR based sex-genotyping.

Gene

target

GenBank accession &

Ensembl ID Forward Primer (5' > 3') Reverse Primer (5' > 3')

Amplicon

length (bp)

TSPY [NC_010462.2]

[XM_003360532.1]

TAGGCCTCAGTCGGTAGTTG TGCTCCTCCTCCTCAAACTC 198

MT-CYB [JN242241.1]

[ENSSSCG00000018094]

CGAAGCTTGATATGAAAAACCATCGTTG AAACTGCAGCCCCTCAGAATGATATTTGTCCTCA 466

Text in parenthesis indicates Ensembl or GenBank reference sequence.

61

Table 2.3. Selected microarray reference genes and calculated gene expression ratio.

Gene

symbol Gene Description Function GER

ACTB Beta-actin [AK237086] Cell motility, structure and integrity 3.2

B2M Beta-2-microglobulin [AK346048];

[XM_003121539]; [ENSSSCT00000005170]; [NM_213978];

[ENSSSCT00000005176]

Cell-surface structure (Human leukocyte

antigen complex – MHC class I)

2.9

GAPDH Glyceraldehyde-3-phosphate dehydrogenase [AK234838] Carbohydrate metabolism

2.2

HMBS Hydroxymethylbilane synthase [ENSSSCT00000016474];

[NM_001097412]

Heme biosynthesis

3.1

HPRT1 Hypoxanthine phosphoribosyltransferase 1

[ENSSSCT00000013865]; [NM_001032376]

Purine ribonucleoside salvage

2.6

SDHA Succinate dehydrogenase complex, subunit A [AK350046] Tricarboxylic acid cycle

2.7

Average 2.8

Standard deviation 0.4

GER = gene expression ratio (log2) of the mean gene expression of the top 50 % (n = 43) compared to the mean gene expression of the bottom 6 % (n = 5) of

pigs. Text in parenthesis indicates Ensembl or GenBank reference sequence.

62

RESULTS

Health Status Evaluation

The health status of all pigs was determined by gross carcass examination at the time of

slaughter. This examination was performed by a Canadian Food Inspection Agency (CFIA) appointed

veterinarian. No samples were collected from animals that did not pass the standard carcass

inspection. The health status of all sampled pigs was further evaluated through microarray expression

data of selected acute phase proteins (haptoglobin, pig MAP/inter-α-trypsin inhibitor, C-reactive

protein, serum amyloid A, ceruloplasmin/ferroxidase and α1-acid glycoprotein/orosomucoid-1)

(Murata et al. 2004). Extensive variation in acute phase mRNA expression was not observed in any of

the pigs studied. The highest and lowest calculated GERs were 5.2 (SAA) and 1.6 (HP) with an

average of 2.9 for all acute phase protein genes (Table 2.4). Acute phase protein mRNA expression

was also evaluated to identify the presence of a subset of pigs with increased mRNA expression as

this would be indicative of an acute phase response; no such subsets were identified in any of the

evaluated acute phase response genes. In addition all of the pigs exhibited a similar pattern of acute

phase protein expression when analyzed by agglomerative hierarchical clustering (Figure 2.1 - Cluster

2). Expression patterns were also similar to those of selected reference genes.

Constitutive Variation in Hepatic Expression of Innate Immune Genes

A total of 114 innate immune genes, identified in the microarray probe set, were ranked

according to their calculated GERs. The ranked GERs of the top (T) 50 % (n = 43) and bottom (B) 6

% of pigs (n = 5) are shown in Table 2.5. Of the 114 genes, three had calculated GERs in excess of

245, namely ATP-dependent DEAD (Asp-Glu-Ala-Asp) box polypeptide 3, Y-linked gene (DDX3Y)

(GER = 2186); mannan-binding lectin C (MBL2) (GER = 741) and secretoglobin, family 1A, member

1 (uteroglobin) (SCGB1A1) (GER = 245). The maximum variation in DDX3Y, MBL2 and SCGB1A1

gene expression between the pig with the highest and lowest microarray expression values was 5900-,

17738- and 1242-fold, respectively. Eighteen genes showed a GER >10; with an additional 29 genes

63

having a GER between 5 - and 10. Another 52 genes had calculated GERs equal to, or less than 5 but

higher than the reference gene with the highest GER (ACTB; GER = 3.2003). The remaining 12 genes

had GER values similar to selected reference genes (Table 2.3 and 2.5). Additionally, GERs were

calculated using different ranking methods (e.g. T 50 % vs. the B 10 % and B 50 % of pigs; the T 20

% vs. the B 20 %; T 10 % and B 10 % of pigs, and the T 6 % vs. the B 50 %), with genes ranked for

each GER, and the average rank calculated (Appendix III). A similar pattern was observed for all

ranking systems, however there were a few exceptions noted when comparing the mean gene

expression of the top 6 % to the bottom 50 % of pigs. Additional genes with a >10-fold change in

expression, using the T 6 %/B 50 % GER, included the complement component C4 precursor

(C4pre), NLR family, pyrin domain containing 5 (NLRP5), NACHT, leucine-rich repeat and PYD

containing 7 Fragment (NLRP7), killer cell lectin-like receptor subfamily A member 1 (LY49), Z-

DNA binding protein 1 (ZBP1), galectin 12 (LGALS12), galectin 3 (LGALS3), pre-pro-beta defensin

104-like (BD104-like) and pre-pro-beta defensin 108-like (BD108-like) (Appendix II). The highest

and lowest calculated GERs for selected reference genes was 3.2 (ACTB) and 2.2 (GAPDH) with an

average of 2.8 for all reference genes (Table 2.3).

Unsupervised agglomerative hierarchical clustering grouped all identified innate immune,

acute phase protein and reference genes into four distinct gene clusters based on their gene expression

patterns (Figure 2.1). The first cluster contained genes where two distinct subpopulations, one with

low and one with high relative mRNA expression could be identified for each gene. Genes within the

second cluster exhibited little variation in relative gene expression. This cluster contained all of the

selected acute phase proteins and reference genes as well as some innate immune genes. The third

cluster was composed of genes where a subpopulation of pigs displayed a marked decrease in relative

mRNA expression. Finally, the fourth cluster consisted of genes where a subpopulation of pigs

showed a marked increase in relative mRNA expression levels. A representative example of each of

the four identified gene expression patterns/clusters is illustrated in Figure 2.2.

A few probes sets with the same gene targets; including LGALS3, galectin 4 (LGALS4),

BD104-like, BD108-like, beta-defensin 123 isoform b (BD123b), complement component 2 (C2),

64

complement component 5a receptor 1 (C5AR1), complement regulator factor H precursor (CFH),

peptidoglycan recognition protein 1 (PGLYRP1), peptidoglycan recognition protein 2 (PGLYRP2) and

ZBP1, did not cluster together and an average expression was not calculated for these gene targets.

Correlation of the mRNA expression of these multiple probes for the same gene target was poorly

correlated. These probe sets had calculated correlation coefficients (R2) ranging from 0.0079 to

0.4395 (Table 2.6).

mRNA expression of selected innate immune genes (MBL2, SCGB1A1, SFTPD, HAMP and

DDX58) was also compared to that of selected acute phase proteins and gene expression was found to

be poorly correlated (Table 2.7).

Sex-Genotyping

In this study we also wanted to identify innate immune genes where the observed variation in

constitutive expression could be explained by differential expression between male and female

individuals. Melting curve analysis of the PCR-amplified fragments generated from the male-specific

TSPY and universal MT-CYB genes was used to differentiate between male pigs that carried both

TSPY (melting point ~ 90.55 ºC) and MT-CYB sequences and female pigs that carried only the MT-

CYB sequence (melting point ~ 81.67 ºC). Forty-nine (55.6 %) of the pigs subjected to sex testing

were identified as males based on the presence of the TSPY gene; the remaining thirty-nine (44.4 %)

of pigs lacked this gene and thus were female. The positive control, MT-CYB, was successfully

amplified from all samples.

There was a significant relationship between sex and the level of mRNA expression as

assessed by microarray analysis of the probe with the highest calculated GER, (microarray probe

annotation - Sus scrofa mRNA, clone:ITT010016G05, expressed in small intestine [AK344932]) and

which corresponded to the Sus scrofa DDX3X gene on the NCBI GenBank database). Male (TSPY-

positive) and female (TSPY-negative) pigs clustered separately with male pigs forming a distinct

cluster of animals that exhibited relatively high levels of mRNA gene expression. Female pigs

65

clustered in a group that exhibited markedly decreased mRNA expression (Figure 2.4). However, the

high level expression of DDX3X in males, observed in this study, and its low level expression in

healthy market weight females was inconsistent with DDX3X being a sexually dimorphic X-linked

gene located in Xp11.3– p11.23 on the X-chromosome (Kim et al. 2001, Park et al. 1998). Alignment

of the microarray probe sequence with the NCBI reference sequence [AK344932] and a number of

other reported DDX3 sequences ([HQ266638.1], [NM_001246203.1], [ENSSSCT00000013398],

[ENSSSCT00000028884]) (Flicek et al. 2013) indicated the microarray gene was in fact the Y-

chromosome ATP-dependent DEAD (Asp-Glu-Ala-Asp) box polypeptide, DDX3Y

(ENSSSCT00000028884) (Flicek et al. 2013). The DDX3Y gene is located in the non-recombining

region of the Y-chromosome (Yq11) and is 91.7 % homologous to the X-linked DDX3X gene with the

microarray probe targeted to this non-homologous region (Lahn and Page 1997, Sekiguchi et al. 2004,

Sekiguchi et al. 2010).

There was no correlation between sex and microarray expression of any of the other identified

innate immune genes (n = 113).

MBL2 Promoter Polymorphisms and their Effect on Hepatic Gene Expression

A subset of eleven pigs with markedly decreased hepatic expression of MBL2 was identified.

This was expected since this study group was selected based on known variations in MBL2 promoter

SNP genotypes. Two polymorphisms in the promoter region of this gene, a MBL2 g.-1091G>A

[previously reported as G(-1081)A] and a MBL2 g.-261C>T SNP [previously reported as C(-251)T],

have been previously identified in our laboratory and linked to altered hepatic expression (Lillie et al.

2007). The presence of the MBL2 g.-1091G>A SNP had a similar effect on microarray gene

expression, as previously reported using semi-quantitative real-time RT-PCR (Lillie et al. 2007)

(Figure 2.5). The Kruskal-Wallis one-way analysis of variance and Dunn’s multiple comparisons post

test was used to identify significant differences in microarray expression between the three MBL2 g.-

1091G>A SNP genotypes (p < 0.0001). Animals that were homozygous (n = 9) for the MBL2 g.-

1091G>A SNP showed a significant decrease in hepatic expression when compared to the wild type

66

allele (n = 47) (p < 0.0001), while expression changes in animals that were heterozygous (n = 32)

were less pronounced (p = 0.1043). Homozygous animals also showed a significant decrease in gene

expression when compared to heterozygous individuals (p = 0.0005). Nine of eleven pigs with the

lowest microarray expression were homozygous for the MBL2 g.-1091G>A promoter polymorphism

(Figure 2.6). The remaining two pigs in this subset were heterozygous for both the MBL2 g.-

1091G>A and MBL2 g.-261C>T promoter SNPs. As previously reported the MBL2 g.-261C>T SNP

had a less profound effect on gene expression. In general, an increase in number of variant SNP

alleles was associated with a decrease in MBL2 gene expression (Figure 2.6).

67

Table 2.4. Selected microarray acute phase protein genes and calculated gene expression ratios.

Gene symbol Gene Description GER

CP Ceruloplasmin (ferroxidase) [ENSSSCT00000012809] 2.3

CRP C-reactive protein, pentraxin-related [ENSSSCT00000007016]; [NM_213844] 4.2

HP Haptoglobin [ENSSSCT00000003046 397061 ]; [NM_214000] 1.6

ITIH4 Inter-α (globulin) inhibitor H4 (plasma Kallikrein-sensitive glycoprotein)/Pig major acute phase

protein (pig-MAP) [ENSSSCT00000012534]; [NM_001001537]

1.8

ORM1 α-1 acid glycoprotein fragment [ENSSSCT00000006034] 2.5

SAA Serum amyloid A2 [ENSSSCT00000014602]; [NM_001044552] 5.2

Average 2.9

Standard deviation 1.4

GER = gene expression ratio (log2) of the mean gene expression of the top 6 % (n = 5) compared to the mean gene expression of the bottom 50 % (n = 43) of

pigs. Text in parenthesis indicates Ensembl or GenBank reference sequence.

68

Table 2.5. Ranking of innate immune genes by variation in constitutive gene expression.

Genes are ranked based on the calculated gene expression ratio (GER). The GER (Log2) for each gene was calculated by comparing the mean gene expression

of the top 50 % (n = 43) of pigs to the bottom 6 % (n = 5) of pigs after excluding high and low expressing outliers (n = 2). Reference genes are shown in bold

and underlined. Text in parenthesis indicates Ensembl or GenBank reference sequence.

Rank GER Gene Symbol Gene Description Rank GER Gene Symbol Gene Description

1 2186.4 DDX3Y ATP-dependent DEAD (Asp-Glu-Ala-

Asp) box polypeptide 3, Y-linked gene

[AK344932]

13 13.3 pPGRP-S Peptidoglycan recognition protein S

[AK231441]

2 740.7 MBL2 Mannan-binding lectin C [NM_214125] 14 13.1 ITLN2 Intelectin 2 [NM_001128453]

3 244.6 SCGB1A1 Secretoglobin, family 1A, member 1

(uteroglobin) [ENSSSCT00000014276]

15 13.1 CLEC1B C-type lectin domain family 1, member

B [ENSSSCT00000000704]

4 43.8 PR39 Peptide antibiotic PR39 [NM_214450] 16 13.1 DDX58 DEAD (Asp-Glu-Ala-Asp) box

polypeptide 58/ Retinoic acid-inducible

gene 1 [NM_213804]

5 40.5 PMAP-23 Porcine myeloid antibacterial protein

PMAP-23 [NM_001129976]

17 12.9 PGLYRP2 Peptidoglycan recognition protein 2

[NM_213738]


PMAP-37 [ENSSSCT00000012426]

18 12.5 PBD-2 Beta-defensin 2 [NM_214442]

7 26.5 NPG4 Protegrin 4 [NM_213863] 19 12.1 PMAP-36 Porcine myeloid antibacterial protein

PMAP-36 [NM_001129965]

8 22.2 SFTPD Surfactant protein D [NM_214110] 20 11.4 SELE Selectin E [NM_214268]


[NM_001001260]

21 10.1 KLRF1 Killer cell lectin-like receptor subfamily

F, member 1 [ENSSSCT00000000711]

10 16.9 HAMP Hepcidin antimicrobial peptide

[NM_214117]

22 9.5 FCN2 Ficolin-β (hucolin) [NM_213868]

11 13.9 LBP Lipopolysaccharide binding protein

[NM_001128435]

23 9.2 BD104-like Pre-pro-beta-defensin 104-like

[BX918848]

12 13.7 MYD88 Myeloid differentiation primary response

gene 88 [NM_001099923]

24 8.9 LGALS12 Galectin 12 [NM_001142844]

69

Table 2.5. continued.


25 8.8 KLRC1 Killer cell lectin-like receptor subfamily

C, member 1 [AJ942142]

39 6.5 BD3 Pre-pro-beta-defensin 3 [NM_214444]

26 8.8 SFTPA1 Surfactant protein A1 [NM_214265] 40 6.2 DDX60 DEAD (Asp-Glu-Ala-Asp) box

polypeptide 60 [XM_001927633]

27 8.8 SELL Selectin L [NM_001112678] 41 6.0 NOD2 Nucleotide-binding oligomerization

domain containing 2 [NM_001105295]

28 8.5 LGALS3 Galectin 3 [NM_001142842] 42 5.9 LGALS13 Galectin 13 [NM_001142841]


(LOC692190), mRNA

[NM_001040641]

43 5.8 CD14 CD14 molecule [NM_001097445]

30 8.0 CLEC7A C-type lectin domain family 7, member

A [ENSSSCT00000000700]


A [ENSSSCT00000000703]

31 7.9 C7 Complement component 7

[NM_214282]


[NM_001097448]

32 7.8 TREM1 Triggering receptor expressed on

myeloid cells 1 [NM_213756]

46 5.6 TLR5 Toll-like receptor 5 [NM_001123202]

33 7.7 C1S Complement component 1, s

subcomponent [NM_001005349]

47 5.5 CLEC4G C-type lectin domain family 4, member

G/ liver and lymph node sinusoidal

endothelial cell C-type lectin

[NM_001144117]

34 7.6 CD302 Type I trans membrane C-type lectin

receptor DCL-1 [TC465837]

48 5.5 C4pre Complement C4 precursor [C4β chain;

C4α chain; C4a anaphylatoxin; C4γ

chain] [TC478078]

35 7.4 NOD1 Nucleotide-binding oligomerization


49 5.3 ZBP1 Z-DNA binding protein 1

[NM_001123216]

36 7.1 TLR4 Toll-like receptor 4 [NM_001113039] 50 5.1 TLR7 Toll-like receptor 7 [NM_001097434]

37 6.6 SELPLG Selectin P ligand [NM_001105307] 51 5.0 LGALS9 Galectin 9 [NM_213932]

38 6.6 KLRB1 Killer cell lectin-like receptor subfamily

B, member 1 [TC451162]

52 4.9 NLRP3 NLR family, CARD domain containing

3 [ENSSSCT00000008719]

70



53 4.9 LY49 Killer cell lectin-like receptor subfamily

A, member 1 [NM_214338]


[NM_001001646]

54 4.8 C5AR1 Complement component 5a receptor 1

[AK344310]


[NM_001097449]

55 4.8 TLR2 Toll-like receptor 2 [NM_213761] 69 4.4 C8A Complement component C8A

[TC447323]

56 4.7 LGALS4 Galectin 4 [NM_213981] 70 4.4 BD103A Beta-defensin 103A precursor

[TC424333]

57 4.7 LEAP2 Liver expressed antimicrobial peptide 2

[NM_213788]

71 4.3 FCN1 Ficolin-α [NM_214160]

58 4.7 TLR10 Toll-like receptor 10 [NM_001030534] 72 4.3 C3 Complement component 3

[NM_214009]

59 4.7 NLRP7 NACHT, leucine-rich repeat and PYD

containing 7 Fragment

[ENSSSCT00000003642]

73 4.2 CD46 CD46 molecule, complement regulatory

protein [NM_213888]

60 4.6 MASP1 Mannan-binding lectin serine peptidase 1

[NM_001184947]



protein [NM_214170]

75 4.2 CD55 CD55 molecule, decay accelerating

factor for complement [NM_213815]

62 4.5 BD123b Beta-defensin 123 isoform b -

HTC438801]

76 4.2 C1qTNF9A Complement C1q tumor necrosis factor-

related protein 9A-like

63 4.5 C4BPA Complement component 4 binding

protein, alpha [NM_213942]


64 4.5 IFIH1 Interferon induced with helicase C

domain 1 (IFIH1)/MDA5

[NM_001100194]


[NM_001101815]


[NM_001163648]

79 4.1 KLRK1 Killer cell lectin-like receptor subfamily

K, member 1 [NM_213813]

66 4.5 NLRP5 NLR family, pyrin domain containing 5

[NM_001163407]

80 4.1 C1esterase Complement C1s subcomponent

precursor (C1 esterase) [TC413063]

71




82 4.0 BD129 Beta-defensin 129 [NM_001129975] 96 3.4 DEFB1 Defensin, beta 1 [NM_213838]


[NM_001123089]


84 4.0 DHX58 DEXH (Asp-Glu-X-His) box

polypeptide 58\RIG-I-like receptor

LGP2 [NM_001199132]

98 3.4 CFD Complement factor D (adipsin)

[ENSSSCT00000014662]

85 3.9 SELP Selectin P [NM_214078] 99 3.3 BD109 Beta-defensin 109 [TC453775]

86 3.9 TLR8 Toll-like receptor 8 [NM_214187] 100 3.3 C1QA Complement component 1, q

subcomponent, A chain

NM_001003924]

87 3.9 MBL1 Mannan-binding lectin A

[NM_001007194]

101 3.3 C8B Complement component C8B

[NM_001097451]


A [TC471307]

102 3.2 C1QB Complement C1qB Fragment

[ENSSSCT00000003919]

89 3.8 LGALS7 Galectin 7 [NM_001142843] N/A 3.2 ACTB Beta-actin [AK237086]

90 3.8 TREM2 Triggering receptor expressed on

myeloid cells 2

[ENSSSCT00000001794]

103 3.2 C1QC Complement component 1, q

subcomponent, C chain

[ENSSSCT00000003916]

91 3.8 CFH Complement regulator factor H

precursor [TC475926]


A [NM_213990]

92 3.7 LGALS8 Galectin 8 [NM_001142827] 105 3.2 C8G Complement component C8G

[AK233484]

93 3.6 BD125 Beta-defensin 125 [NM_001129974] N/A 3.1 HMBS Hydroxymethylbilane synthase

[ENSSSCT00000016474];

[NM_001097412]

94 3.6 KLRG1 Killer cell lectin-like receptor subfamily

G, member 1 [ENSSSCT00000000719]

106 3.1 NLRC5 NLR family, CARD domain containing

5/ Nucleotide-binding oligomerization

domain containing 4 [EU350951]

72



107 3.0 CFP Complement factor properdin

[ENSSSCT00000013427] N/A 2.6 HPRT1 Hypoxanthine

phosphoribosyltransferase 1

[ENSSSCT00000013865];

[NM_001032376]

108 2.9 BD122 Beta-defensin 122 [TC499283] N/A 2.2 GAPDH Glyceraldehyde-3-phosphate

dehydrogenase [AK234838]

N/A 2.9 B2M Beta-2-microglobulin [AK346048];

[XM_003121539];

[ENSSSCT00000005170];

[NM_213978];

[ENSSSCT00000005176]


A [TC453642]

109 2.7 BD114 Beta-defensin 114 [NM_001129973] 112 2.0 BD121 Defensin, beta 121

[ENSSSCT00000007900]

110 2.7 BD4 Pre-pro-beta-defensin 4 [NM_214443] 113 1.8 C1r Complement component 1, r

subcomponent [ENSSSCT00000000733]

N/A 2.7 SDHA Succinate dehydrogenase complex,

subunit A [AK350046]

114 1.7 CFB Complement factor B [NM_001101824]

73

Table 2.6. List of innate immune genes with multiple microarray probes with poor internal probe correlation.

The listed microarray probes failed to cluster together using unsupervised hierarchical agglomerative clustering. Comparison of the mRNA expression of each

probe set showed poor correlation between probes targeting the same gene.

Gene target Gene symbol Number of probes Correlation coefficient (R2)

Beta-defensin 123 isoform b BD123b 2 0.3122

Complement component 2 C2 2 0.4395

Complement component 5a receptor 1 C5AR1 2 0.3498

Complement regulator factor H precursor CFH 2 0.1074

Galectin 3 LGALS3 9 0.0079 – 0.2687*

Galectin 4 LGALS4 2 0.2970

Peptidoglycan recognition protein 1 PGLYRP1 2 0.1743

Peptidoglycan recognition protein 2 PGLYRP2 2 0.3405

Pre-pro-beta defensin 104-like BD104-like 2 0.1176

Pre-pro-beta defensin 108-like BD108-like 2 0.0841

Z-DNA binding protein 1 ZBP1 2 0.3331

* minimum and maximum calculated R2 values of all possible probe comparisons.

74

Table 2.7. Constitutive variation in innate immune gene expression is not correlated with acute phase protein expression.

Microarray expression (relative to GAPDH) of some of the innate immune genes that exhibited widely variable constitutive hepatic gene expression was

compared to the expression of selected acute phase proteins. The expression of these innate immune genes was poorly correlated with the expression of all

acute phase proteins (correlation coefficient R2)

Correlation coefficient (R2)

Ceruloplasmin

(CP)

C-reactive protein

(CRP)

Haptoglobin

(HP)

Pig-MAP

(ITIH4)

Orosomucoid-1

(ORM1)

Serum amyloid A

(SAA)

MBL2 0.0010 0.0092 0.0031 0.0286 0.0179 0.0130

SCGB1A1 0.0051 0.0121 0.0137 0.0028 0.0097 0.0044

SFTPD < 0.0001 0.0031 < 0.0001 0.0182 0.0009 0.0048

HAMP 0.0003 0.0116 0.0124 0.0057 0.0269 0.0044

DDX58 0.0638 0.0261 0.0370 0.0575 0.0252 < 0.0001

75

357

514

27

317

743

5 300

150

909

709

767

903

379

568

105

284

587

708

136

782

609

698

556

705

704

10

406

947

596

389

1001

197

143

232

104

447

120

470

25

477

446

811

948

781

98

670

892

694

388

398

830

873

192

615

622

1 925

961

319

794

799

63

236

352

983

307

573

932

601

321

599

399

887

636

135

487

263

859

512

286

434

339

213

248

253

812

244

692

DDX3YMBL2HAMP AVGPGLYRP2 AC5AR1 ACD46PBD-2TLR7NOD1TLR6BD 108-like 1BD 123b 2NLRP3TREM2PMAP-36PMAP-37PGLYRP1 APR39NPG4 AVGPMAP-23FCN1TREM1BD 104-like 1BD 109CD55 AVGLGALS3 AVG1ITIH4 AVGLBPCRPSAA AVGFCN2 AVGLEAP2CFD AVGLGALS1 AVGKLRK1TLR1ORM1ProperdinGAPDHCLEC14ACD302TLR3 AVGC8BC4BPA AVGSDHA AVGC5 AVGC6 AVGCP AVGC4 AVGC2 AC8G AVGC1s AVGC3 AVGHP AVGCD14 AVGC1QAC1QBC1QCTLR2C9 AVGMASP2 AVGCFH 1MBL1ACTB AVGC8A AVGB2M AVGHPRT1LGALS8 AVGHMBS AVGC1rCFBC5AR1 BMYD88PGLYRP2 BTLR5CLEC4GC1 esteraseC2 BC7MASP1 AVGIFIH1/MDA5 AVGLGALS9 AVGZBP1 ADDX60 AVGDDX58 AVGDHX58KLRG1TLR9BD125KLRB1 AVGNLRC5NOD2 AVGDEFB1BD 103ABD 123b 1BD129 AVGSELPTLR10SELL AVGCD59 AVGTLR4 AVG1TLR8CLEC1ACLEC7A AVGKLRF1BD 122LGALS4 BSCGB1A1KLRC1BD 121SFTPDBD 3CLEC1BSFTPA1 AVGPGLYRP1 BLGALS4 ALGALS7 AVGLY49 AVGCLEC5ACFH 2BD 4CLEC16AZBP1 BBD 104-like 2LGALS12 AVGC1qTNF9AITLN2 AVGBD 108-like 2pPGRP-S AVGLGALS3 AVG2C4 preNLRP5BD114NLRP7SELPLGLGALS13SELE AVG

-3.0 -2.8 -2.6 -2.4 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.4 2.6 2.8 3.0

357

514

27

317

743

5 300

150

909

709

767

903

379

568

105

284

587

708

136

782

609

698

556

705

704

10

406

947

596

389

1001

197

143

232

104

447

120

470

25

477

446

811

948

781

98

670

892

694

388

398

830

873

192

615

622

1 925

961

319

794

799

63

236

352

983

307

573

932

601

321

599

399

887

636

135

487

263

859

512

286

434

339

213

248

253

812

244

692


-3.0 -2.8 -2.6 -2.4 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.4 2.6 2.8 3.0

357

514

27

317

743

5 300

150

909

709

767

903

379

568

105

284

587

708

136

782

609

698

556

705

704

10

406

947

596

389

1001

197

143

232

104

447

120

470

25

477

446

811

948

781

98

670

892

694

388

398

830

873

192

615

622

1 925

961

319

794

799

63

236

352

983

307

573

932

601

321

599

399

887

636

135

487

263

859

512

286

434

339

213

248

253

812

244

692


-3.0 -2.8 -2.6 -2.4 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.4 2.6 2.8 3.0

357

514

27

317

743

5 300

150

909

709

767

903

379

568

105

284

587

708

136

782

609

698

556

705

704

10

406

947

596

389

1001

197

143

232

104

447

120

470

25

477

446

811

948

781

98

670

892

694

388

398

830

873

192

615

622

1 925

961

319

794

799

63

236

352

983

307

573

932

601

321

599

399

887

636

135

487

263

859

512

286

434

339

213

248

253

812

244

692


-3.0 -2.8 -2.6 -2.4 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.4 2.6 2.8 3.0

Cluster 1

Cluster 2

Cluster 3

Cluster 4

76

Figure 2.1. Unsupervised agglomerative hierarchical clustering of innate immune gene

expression.

Four distinct expression patterns/clusters of innate immune genes were observed.

Cluster 1: This gene cluster contained genes where the relative mRNA expression varied from very

low to high and subpopulations with increased and decreased expression can be identified.

Cluster 2: Variation in gene expression in the second cluster was less pronounced with a small

subpopulation of pigs exhibiting low relative gene expression. This cluster contains selected acute

phase proteins, reference genes and some innate immune genes.

Cluster 3: This cluster is composed of genes where a subpopulation of pigs displayed a marked

decrease in mRNA expression.

Cluster 4: Genes in this cluster contain a subpopulation of pigs with markedly increased mRNA

expression levels.

77

Figure 2.2. Microarray

expression of representative

examples of the four distinct

expression pattern/clusters.

A: Hepcidin (HAMP)

expression ranged from low to

high and two distinct

subpopulations of pigs with

increased and decreased

mRNA expression is observed.

B: Variation in mRNA

expression of the acute phase

protein haptoglobin (HP) was

less pronounced.

C: A subpopulation of pigs

with markedly decreased

expression of RIG-1 (DDX58)

can be identified.

D: A subpopulation of pigs

with markedly increased

expression of NLR family,

pyrin domain containing 5

(NLRP5) can be identified.

Each diamond represents the microarray expression of each target gene in an individual pig relative to GAPDH.

78

Figure 2.3. Melting curve analysis of the TSPY and MT-CYB duplex sex-genotyping assay.

Melting curve analysis was used to identify animals that expressed both the TSPY and MT-CYB genes (male indicated in blue) vs. those that only expressed

the MT-CYB gene (female indicated in red). The melting temperatures of the TSPY and MT-CYB genes were 90.55 ºC and 81.67 ºC, respectively.

79

Figure 2.4. Normalized microarray expression of DDX3Y.

Two distinct stratified subpopulations of high and low expression are observed. High expressing animals were identified as males (blue) and low expressing

animals as females (red). Each diamond represents the expression of DDX3Y in an individual pig relative to GAPDH.

80

Figure 2.5. Hepatic expression of MBL2 in MBL2 g.-1091G>A SNP genotypes measured by microarray and semi-quantitative real-time RT-PCR.

Homozygous animals (n = 9) showed a significant decrease in hepatic microarray expression of MBL2 when compared to both the wild type allele (n = 47) (p

< 0.0001) and heterozygous individuals (n = 32) (p = 0.0005). Heterozygous animals also had a decreased mean microarray gene expression when compared

to the wild type allele however this change was less pronounced (p = 0.1043). RT-PCR data modified from (Lillie et al. 2007). * indicates a significant

difference at p < 0.05.

81

Figure 2.6. Microarray expression of MBL2.

A distinct subpopulation of pigs with decreased mRNA expression of MBL2 was identified. Nine out of eleven animals with the lowest MBL2 expression

levels contained the MBL2 g.-1091G>A promoter polymorphism. The MBL2 g.-261C>T SNP was also associated with decreased expression of MBL2,

although to a lesser extent. Each diamond represents the expression of MBL2 in an individual pig relative to GAPDH.

82

DISCUSSION

The use of high through-put sequencing and whole genome microarray analysis have been

particularly informative when applied to gene expression profiling of specific tissues and/or cell types

(Carninci et al. 2005, Su et al. 2002, Su et al. 2004). The expression profiles generated by analyzing

samples from healthy individuals and animal species can be used to establish a reference network,

pattern or atlas of gene expression for a given tissue or cell type (Freeman et al. 2012, Lukk et al.

2010). Comparison of these profiles to those obtained from diseased tissues and cells provides a

powerful approach for identifying the genetic defects that result in increased disease susceptibility and

pathogenesis (Ge et al. 2005, Lukk et al. 2010). Most porcine studies have focussed on genes that are

differentially expressed following experimental or natural infection with a limited number of

pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus

type 2 (PCV2) and post-weaning multi-systemic wasting syndrome (PMWS), Actinobacillus

pleuropneumoniae (APP), E. coli F18, classical swine fever (CSF), lipopolysaccharides,

Streptococcus equi subsp. zooepidemicus and other bacterial pneumonias (Bao et al. 2012, Fernandes

et al. 2012, Gladue et al. 2010, Hedegaard et al. 2007, Lee et al. 2010, Li et al. 2010, Li et al. 2013,

Ma et al. 2012, Mortensen et al. 2011, Moser et al. 2004, Moser et al. 2008, Sanz-Santos et al. 2011,

Skovgaard et al. 2010, Tomas et al. 2010, Wysocki et al. 2012, Zuo et al. 2013) while some studies

have also compared expression patterns during different physiological states such as pregnancy,

lactation or following muscle exertion (Jensen et al. 2012, Ostrup et al. 2010, Shu et al. 2012).

Although these studies have advanced our understanding of the porcine transcriptome and the innate

response in pigs, there are still significant gaps in our understanding of constitutive variation in gene

expression in different tissue and cell types. In one recent study, Freeman et al. applied microarray

expression technology to 62 different porcine tissues and cell types (Freeman et al. 2012). Analysis of

large sample sizes is especially important when examining the relationship between genetic variation

and gene expression, as observed in studies of mannan-binding lectin C in humans and pigs (Garred et

al. 2003, Lillie et al. 2007, Madsen et al. 1998). Although the Freeman study serves as an important

resource, it was limited to four animals (one male and three females), making it difficult to extrapolate

83

the results to different pig populations, especially for the evaluation of constitutive variation in gene

expression.

To our knowledge, this is the first study to use whole genome microarray technology to

specifically quantify constitutive variation in the expression of innate immune genes in any tissue or

species. Using this approach, we measured the constitutive expression of a number of innate immune

proteins (n = 114), 21 (18.4 %) of which exhibited a >10-fold decrease (or increase) in hepatic

expression. The gene expression ratio (GER) for these genes, as measured by the mean expression of

the top 50 % compared to the bottom 6 % of pigs, varied from 0 to > 2186. An additional nine genes

(7.9 %) with a GER > 10-fold were identified by comparing mean expression levels in the top 6 % to

the bottom 50 % of pigs, an approach that is more suitable for the detection of a subpopulation with

increased levels of expression. The maximum difference in gene expression between the pig with the

lowest and highest mRNA levels was 17 738 fold in MBL2.

A few of the genes identified in our study have been previously studied in human and/or

porcine tissues, one of which is MBL2. Polymorphisms in the promoter region of human MBL2 have

been previously linked to decreased circulating levels of MBL-C (Garred et al. 2003, Madsen et al.

1998). We found that pigs that were homozygous for MBL2 g.-1091G>A exhibited a significant

decrease in MBL2 gene expression while pigs that were heterozygous for this SNP exhibited a similar,

but less profound decrease. A second SNP, MBL2 g.-261C>T, was also associated with lower levels

of MBL2 expression but the decrease was less profound than that observed for MBL2 g.-1091G>A.

These results are consistent with a previous RT-PCR study showing an association between MBL2 g.-

1091G>A and MBL2 g.-261C>T and reduced hepatic expression of porcine MBL2 (Lillie et al. 2007).

This high degree of concordance between methods and studies support our hypothesis that microarray

technology in combination with sequencing can be used to identify novel polymorphisms (SNPs,

insertions, deletions) associated with altered expression of innate immune genes.

When analyzed using unsupervised agglomerative hierarchical clustering, the 114 genes

identified in this study fell into four distinct clusters (Figure 2.1 and 2.2). The proteins and receptors

within each cluster had similar patterns of gene expression and many, but not all, had similar

functional properties. Cluster 1 was composed of innate response proteins that were highly variable

84

among individual pigs. This expression group contained a number of antibacterial peptides (NPG4,

PR39, PMAP-23, PMAP-36 and PMAP-37) and other neutrophil granule associated molecules

(PGLYRP1 probe A).

Cluster 2 consisted of genes that showed little variation between individual pigs and

occasionally a subpopulation of pigs with decreased relative expression could be identified. In

addition to complement components (C1S, C8G, C2 probe A, C3, C4, C5, C6, C9, C4BPA, C8B,

C1QA, C1QB and C1QC), this cluster contained the acute phase proteins [ITIH4 (pig-MAP); SAA

(serum amyloid A); CRP (c-reactive protein); HP (haptoglobin), CP (ceruloplasmin/ferroxidase) and

ORM1 (α1-acid glycoprotein/orosomucoid-1)] and all of the selected reference genes, (HMBS,

HPRT1, B2M, ACTB, GAPDH and SDHA). The lack of variation in expression of acute phase

proteins, absence of a subset of pigs with elevated acute phase gene expression and the similarity of

gene expression to that of selected reference genes suggests none of the pigs had an acute phase

response at the time of sampling and were thus healthy, a finding that was consistent with the clinical

evaluation of these healthy pigs. The lack of correlation between expression of the selected acute

phase proteins and that of innate immune genes with widely variable constitutive expression is

indicative that these genes are not coordinately expressed (Table 2.7). This finding was of particular

importance in ruling out the possibility that the observed variations in gene expression were due to

infection and inflammation rather than differences in constitutive expression.

Cluster 3 consisted of proteins that often contained markedly reduced expression in a subset

of pigs and included the antiviral signaling RLR helicases DDX58 (RIG-1), IFIH1 (MDA-5), DHX58

(LGP2), ZBP1 probe A (DAI) and DDX60.

In contrast, cluster 4 was composed of genes that often contained markedly increased

expression in a subset of pigs, including the pulmonary C-type lectins SFTPD and SFTPA1 as well as

SCGB1A1, a secretory protein better known as being expressed in Clara cells of the lung.

The mRNA expression of a few target genes with multiple probes, LGALS3, LGALS4,

BD104-like, BD108-like, BD123b, C2, C5AR1, CFH, PGLYRP1, PGLYRP2 and ZBP1, did not cluster

together within any of the four expression groups (Table 2.6). mRNA expression results when

analyzed using multiple targeted probes directed against different regions of the full length mRNA

85

transcript for these genes gave discrepant results. A possible reason for discrepant results may relate

to the potential for differential degradation of the mRNA template. Although every possible effort was

made to ensure that our RNA was intact and of the highest quality (i.e. all of our samples had an RIN

number > 7.0), mRNA is easily degraded by a number of different mechanisms. The majority of

eukaryotic mRNA degradation is initiated by shortening of the 3' polyadenosine tail (deadenylation).

After deadenylation mRNA is then further degraded by either exonucleolytic decapping of the 5'-cap

structure and 5' to 3' degradation (Coller and Parker 2004, Hu et al. 2009, Parker 2012, van Hoof and

Parker 2002). Additionally mRNA degradation can also occur in the 3' to 5' direction, which is

mediated by the cytoplasmic exosome 1 (Coller and Parker 2004, Hu et al. 2009, Parker 2012, van

Hoof and Parker 2002). Preferential degradation of the 3'- (or 5'-) end of the mRNA could, in theory,

give discordant results when using probes directed against these different gene regions. Although

most of these poorly correlated probes were designed to target the 3'-end of the mRNA, some probes

were located toward the 5'-end with an occasional probe spanning an intron and distance between

mRNA probes did not appear to be associated with the observed variation in correlation in this study.

Other more targeted degradation factors such as miRNA may also play a role in determining the

amount of mRNA that is available for quantification (Deneke et al. 2013, Huntzinger and Izaurralde

2011). MicroRNA (miRNA), transcriptional and post-transcriptional regulation, pre-mRNA splicing

and post-splicing RNA processing as well as post-translational modifications and DNA methylation

have all been shown to have a significant effect on mRNA production and final protein product

concentrations (Bartel 2004, Fire et al. 1998, Huntzinger and Izaurralde 2011, Xiao et al. 2012, Yang

and Seto 2008, Ye et al. 2012)

A potential limitation inherent in gene expression studies performed on tissue lysates relates

to the heterogeneity of the sample. Although hepatocytes are the most abundant cell type in the liver

and contributes the most of the cytoplasmic mass and therefore represent a major source of innate

immune response proteins, other cell types such as macrophages, dendritic and Kupffer cells,

fibroblasts, vascular endothelial and biliary epithelial cells, as well as circulating cells within the

vascular compartment of the liver may also contribute to the “global” gene expression patterns

86

observed in our study. The presence of different functional units and zones within hepatic acini and

differences in blood flow to and from different regions and lobes of the liver may also have an effect

on the cellular composition of the liver and the relative contribution of different cell types to the

observed transcriptome patterns. However, variations in these factors among individual pigs should be

minimal and would not be expected to account for the large increases (>245-fold) in mRNA observed

for genes such as MBL2 and SCGB1A1. It is possible, however, that some of the variation observed

for granulocyte associated porcine cathelicidins and peptidoglycan recognition proteins which are

known to be primarily expressed in leukocytes (PR-39, protegrins, porcine myeloid antibacterial

peptides/PMAPs and PGLYRP1) (Dziarski and Gupta 2010, Sang and Blecha 2009) may be due to

differences in blood flow and circulatory constituents. A number of growth promotants, including

antibiotics and repartitioning agents such as Ractopamine, are registered for use in swine, some of

which have short or no withdrawal periods and can be used up to the time of slaughter. In swine,

Ractopamine has been shown to alter gene expression in both white adipose tissue and muscle

(Gunawan et al. 2007, Halsey et al. 2011). Similarly in chickens antibiotics such as Bacitracin has

been shown to alter gene expression of genes in the jejunum of chickens and a similar situation likely

exists in swine (Brennan et al. 2013). The use of such products immediately up to the time of

slaughter can therefore represent a potential limiting factor, especially if such drugs are used

inconsistently between different production units. It is currently unknown if similar alterations in gene

expression would be observed in the liver or whether or not these products would specifically alter the

expression of innate immune genes.

Knowledge of the porcine genome is still in its infancy and, as a result, the probe annotations

used to design commercially available porcine microarrays are continually being improved. As a

result of limited information, inaccurate gene designations may occur as described for DDX3Y. Some

studies have shown that up to 50 % of the oligonucleotide probes in some commercial microarray

platforms can give erroneous results either through cross hybridization with other probes, lack of

target specificity and/or the presence of orphan probes that target genes that do not exist in the target

genome under evaluation (Neerincx et al. 2009). These pitfalls can affect downstream data analysis

87

and lead to erroneous identification of differentially expressed genes. Splice variants can also pose a

potential for error if probes are not designed to differentially quantify all known variants in the target

sequence. This can have a significant effect on inter-platform reproducibility and even on updated

versions of the same platform (Lee et al. 2007).

Splice variants may account for some of the poor probe correlations and divergent clustering

observed in these studies for LGALS3, C2, CFH, PGLYRP2 and ZBP1, all of which code for two or

more transcript variants (Flicek et al. 2013). This may indeed be the case for the PGLYRP2, a protein

that has two different characterized splice variants. The long isoform is expressed predominantly in

the liver, whereas the short isoform is expressed in bone marrow, intestine, spleen, kidney, and the

skin, in addition to liver (Sang et al. 2005). One of the probes recognizes both mRNA isoforms

whereas the second probe recognizes the long [ENSSSCT00000022764] but not the short isoform

[ENSSSCT 00000023031].

A number of software programs have been developed to aid in improving probe annotation

for microarray experiments. These programs, such as IMAD, OligoRAP and sigReannot have been

shown to significantly improve probe annotation and downstream GO term enrichment analyses

(Casel et al. 2009, Neerincx et al. 2009, Neerincx et al. 2009, Prickett and Watson 2009). In addition,

a number of online probe annotation tools have also been developed to support some domestic

animals including GOEAST (http://omicslab. genetics.ac.cn/GOEAST/), Blast2GO

(http://www.blast2go.de/b2ghome), EasyGO (http:// bioinformatics.cau.edu.cn/easygo/) and AgriGo

(http://bioinfo.cau.edu.cn/agriGO/) (Conesa et al. 2005, Du et al. 2010, Zheng and Wang 2008, Zhou

and Su 2007). However, not all programs support all available platforms and in the current study

further annotation of the Agilent porcine microarray platform could not be performed with currently

available software programs. In this study, we identified 114 innate immune genes based on currently

available information. Additional annotations are needed to extend this work to a larger number of

target genes.

88

Since none of the genes in the porcine microarray assay have been annotated for sex, we

investigated whether ATP-dependent DEAD (Asp-Glu-Ala-Asp) box polypeptide, DDX3Y, could be

used a sex-genotyping tool. Selection of this gene was based on the marked variation observed in

mRNA expression and stratification thereof into two distinct groups of high and low expression. This

distinct stratification and strong correlation with our PCR based sex-genotyping assay suggest that

when a microarray platform containing the annotated DDX3Y gene is used, microarray expression of

this gene represents a useful sex-genotyping tool in studies where this information is unknown.

Alternatively DDX3Y can also be used as a gene target to design real-time RT-PCR based sex-

genotyping assays, as described for TSPY and CYB1 in this study. Both the X- and Y-linked homologs

are intracellular RNA sensing PRRs that play an important role in innate antiviral signalling and viral

pathogenesis (Garbelli et al. 2011, Owsianka and Patel 1999, Schroder 2011, Soulat et al. 2008).

Although this gene showed one of the highest calculated GERs, variation in expression in this case

was considered to be due to the sexual dimorphic nature of this Y-chromosome linked gene.

Using genome wide expression microarray technology we were able to identify a number of

innate immune genes that exhibited wide variation in constitutive expression. These innate immune

genes represent important targets for further investigation aimed at identifying the factors that

underlie the observed variation. As was shown with MBL2, sequencing the regulatory regions of these

target innate immune genes should lead to the identification of genetic differences (SNPs, insertions,

deletions or other genetic variations) that are associated with the wide variation observed. Ultimately

the identification of such genetic markers could be used to breed healthy pigs with higher levels of

innate resistance to common infectious diseases. Additionally the opportunity also exists to apply the

same methods in other immunologically important tissues such as the lung or spleen to identify

additional target innate immune genes. The same techniques can also be applied to study constitutive

gene expression of other genes affecting economically important traits such as genes involved in

metabolism, fertility and/or production characteristics.

89

CHAPTER 3: NOVEL PROMOTER POLYMORPHISMS ASSOCIATED WITH

INCREASED CONSTITUTIVE EXPRESSION OF SCGB1A1 AND SFTPD mRNA IN THE

LIVER OF HEALTHY PIGS


authorship:

Snyman HN, Jagt K, Hammermueller JD, Hayes MA, Lillie BN (2013)

ABSTRACT

The innate immune system represents an important component of the host defence against

infectious diseases and alterations in the expression of critical innate immune genes, such as those

resulting from underlying genetic variations, have been associated with increased susceptibility to

developing infectious diseases in pigs. Previous studies identified a number of innate immune genes

with marked variability in constitutive expression. Two of the genes that showed the greatest increase

in mRNA expression were two genes involved in innate immunity in the lung, pulmonary surfactant

protein D (SFTPD), a member of the collectin family of C-type lectins and secretoglobin family 1A

member 1 (SCGB1A1), a secretory protein expressed in Clara cells of the lung. In this study, we

characterized the 5' upstream promoter regions of these genes to determine if genetic differences are

responsible for the variation in constitutive expression. Using pooled sequencing of the lowest and

highest expressing animals, we identified three novel single nucleotide polymorphisms, SFTPD g.-

4509A>G, SFTPD g.-4394G>A and SFTPD g.-4350C>T within the 2682 bp of the 5'-promoter

region of SFTPD. A novel polymorphic sequence with a large number of variations was also

identified in the 1953 bp of the 5' promoter region of SCGB1A1 and may be indicative of duplication

of the SCGB1A1 gene. All three SFTPD SNPs and the polymorphic SCGB1A1 gene were more

frequent in pigs with increased mRNA expression. The SFTPD g.-4509A>G SNP was rare throughout

all healthy and diseased genotyped populations. Although no statistically significant disease or

etiologic agent associations were identified for this SNP, variant genotype frequency was increased

two- to four- fold in pigs infected by a variety of pathogens associated with lung disease. These

90

findings suggest that these SNPs are associated with a gain in function of SP-D. This sets the stage for

future investigations into the significance of these polymorphisms on innate immune defenses and

ultimately may serve as genetic markers to assess and improve innate disease resistance in

commercial swine populations.

91

INTRODUCTION

Abnormalities in gene expression and function resulting from specific genetic polymorphisms

within some innate immune genes of humans and domestic animals have been shown to have a

detrimental effect on host susceptibility to common infectious diseases (Garred et al. 2003, Garred

and Madsen 2004, Garred et al. 2006, Ibeagha-Awemu et al. 2008, Jozaki et al. 2009, Juul-Madsen et

al. 2011, Keirstead et al. 2011, Leth-Larsen et al. 2005, Lillie et al. 2006, Lillie et al. 2007, Madsen et

al. 1998, Uenishi et al. 2011, Uenishi et al. 2012, Wang et al. 2011, Zhao et al. 2012). In pigs, some of

these polymorphisms have been shown to significantly alter gene expression and may involve regions

involved in transcriptional regulation (Juul-Madsen et al. 2006, Juul-Madsen et al. 2011, Lillie et al.

2006, Lillie et al. 2007). The identification of additional polymorphisms (SNPs, insertions, deletions

or other genetic variations) that affect the transcriptional regulation of innate immune genes may lead

to novel selection strategies that can be used to increase resistance to infectious diseases in swine. We

recently conducted a genome-wide study of hepatic gene expression in healthy market weight pigs

using microarray technology to identify innate immune genes with widely variable constitutive gene

expression (Chapter 2). Two genes associated with pulmonary innate immunity showed among the

greatest variation in mRNA expression. One of these was pulmonary surfactant protein D (SP-D;

encoded by SFTPD), a pattern recognition molecule and member of the collectin family of C-type

lectins and the second was secretoglobin family 1A member 1 (SCGB1A1, encoded by SCGB1A1), a

secretory protein expressed in Clara cells of the lung (Haagsman et al. 2008, Mukherjee et al. 2007).

Both SP-D and SCGB1A1 have been shown to play an important role in the immune

modulation of innate immune responses to pulmonary pathogens (Haagsman et al. 2008, Mukherjee et

al. 2007).; The role of SP-D, along with the related SP-A, in pulmonary innate defense has been

extensively reviewed (Creuwels et al. 1997, Haagsman et al. 2008, Hartl and Griese 2006, Kuroki et

al. 2007, McCormack and Whitsett 2002). SP-D is produced primarily in alveolar type II cells and

nonciliated bronchiolar cells of the lung and is constitutively secreted into the alveoli where it

influences surfactant homeostasis, effector cell functions and host defense (Herias et al. 2007, Madsen

et al. 2000). SP-D binds to sugar moieties on the surface of bacterial, viral and fungal pathogens via

92

its carbohydrate recognition domain (CRD) (Chapter 1; Table 1.2), a process that leads to the

agglutination and opsonisation of pathogens followed by phagocytic uptake and clearance (Creuwels

et al. 1997, Hartl and Griese 2006, Kuroki et al. 2007). SFTPD is located within the collectin locus on

Sus scrofa chromosome 14 along with SP-A and mannan-binding lectin-A (MBL-A) (Marklund et al.

2000, van Eijk et al. 2000). SP-D is a trimeric molecule composed of three identical monomeric

polypeptide units (Holmskov et al. 2003) and has a higher order oligomeric cruciform structure

composed of at least four trimeric subunits. Although alveolar type II cells and mucosal surface

epithelium are the major sites of SFTPD expression, expression in a variety of other organs including

other cells in the lungs as well as, liver, kidney and ovary has been reported (Hartl and Griese 2006,

Herias et al. 2007, Madsen et al. 2000, Skovgaard et al. 2010).

SCGB1A1 is found in secretory granules of Clara cells and is one of the most abundant

proteins in airway secretions (Singh and Katyal 2000). SCGB1A1 was originally isolated from early

gravid rabbit uteri and named blastokinin and later uteroglobin (Beier 1968, Krishnan and Daniel

1967). Since then the protein has been isolated from a variety of biological sources and, as a result,

was given various names including Clara cell secretory protein (CCSP), Clara cell 10 kDa protein

(CC10), CC16 and urine protein-1 (UP1) before becoming the founding member of the secretoglobin

superfamily (Mukherjee et al. 2007). SCGB1A1 has many functional properties and, although the

structural features of this protein have been extensively studied, the mechanisms underlying the

protein’s various functions have not been fully elucidated (Callebaut et al. 2000, Pattabiraman et al.

2000, Singh and Katyal 2000). SCGB1A1 has been implicated in a number of anti-inflammatory and

immunomodulatory processes and has been shown to sequester and bind hydrophobic ligands such as

phosphatidylcholine and phosphatidylinositol and also inhibit secretory phospholipase A2 and the

recruitment of leukocytes (de la Cruz and Lee 1996, Singh and Katyal 2000, Wong et al. 2009). Based

on shared structural features with colicin A, an antibacterial protein produced by Escherichia coli, it

has been proposed that SCGB1A1 has similar direct antibacterial functions (de la Cruz and Lee 1996).

Although SCGB1A1 expression has been most extensively studied in lung and endometrial tissue,

93

variable levels of expression have been detected in a variety of other tissues including the liver (Cote

et al. 2012, Peri et al. 1993).

In this study, we characterized the 5'-promoter regions of SFTPD and SCGB1A1 to determine

if there was a genetic basis to the wide variation in constitutive hepatic expression observed. Several

novel SNPs and polymorphisms were identified that were correlated with increased hepatic

expression of these proteins. Restriction fragment length polymorphism (RFLP) assays were

developed to genotype pigs for the identified SFTPD SNPs. Variant genotype frequencies for the

SFTPD g.-4509A>G SNP was also compared in healthy and diseased pig populations.


Sample Acquisition, Nucleic Acid Extraction and Primer Design

Liver samples of 1003 healthy terminally crossed commercial market weight pigs were

collected from a large southern Ontario pig processing facility as described in Chapter 2.

Nucleic acids were extracted from the livers of a subset of 88 pigs that had been previously

subjected to microarray expression analysis and stored as described in Chapter 2.

Primers for PCR amplification were designed based on genomic sequences available in the

Ensembl online genome browser (Flicek et al. 2013) and NCBI GenBank

(http://www.ncbi.nlm.nih.gov/gene) databases. Primers were designed using a combination of

Primer3 v. 4.0.0 (http://primer3.wi.mit.edu/) (Rozen and Skaletsky 2000); Generunner

(http://www.generunner.net); Primer-Blast (http://www.ncbi.nlm.nih.gov/ tools/primer-blast/);

PrimerQuest (http://www.idtdna.com/Primerquest/Home/Index) and OligoAnalyzer

(http://www.idtdna.com/analyzer/Applications/Oligo Analyzer/).

94

Amplification of the 5'-Promoter Regions of SCGB1A1 and SFTPD

Gene segments, 2362 and 2682 bp in length were amplified from 5'-promoter regions of

SCGB1A1 and SFTPD, respectively, using the forward and reverse primers listed in Table 3.1. PCR

reactions for SCGB1A1 (50 μL) were performed according to the manufacturers recommendations

using the QIAGEN TopTaq DNA Polymerase Kit®, and a final primer concentration of 0.5 µM.

Cycling parameters were as follows: initial denaturation for 3 min at 94 ºC, followed by 35 cycles of

denaturation at 94 ºC for 30 s, annealing at 59 ºC for 30 s and extension at 72 ºC for 2 min and 25 s,

with a final extension of 72 ºC for 10 min. PCR reactions for SFTPD (50 μL) were performed

according to the manufacturers recommendations using the MyTaqTM

DNA polymerase kit (Bioline,

Taunton, MA) and a final primer concentration of 0.4 µM. Cycling parameters for SFTPD were:

initial denaturation for 2 min at 95 ºC, followed by 40 cycles of denaturation at 95 ºC for 20 s,

annealing at 62 ºC for 20 s and extension at 72 ºC for 2 min, with a final extension of 72 ºC for 5 min.

All PCR products in this study were visualized on agarose gels (1 or 2 %) in 0.5 X tris-borate-

EDTA (TBE) buffer stained with SYBR SAFE nucleic acid stain.

Sequencing of PCR products and Identification of Novel SNPs.

PCR products amplified from pigs with the highest (n = 8) and lowest (n = 8) levels of

mRNA expression, as determined by microarray analysis, were purified and pooled into four groups.

The pooled samples, each group consisting of four individual PCR products, were then submitted for

automated sequencing (Lab Services Division, University of Guelph, Guelph, Ontario). Within some

amplification reactions for SCGB1A1, two PCR products were amplified. In these cases, each band on

the agarose gel was purified using the QIAquick® gel extraction kit (QIAGEN, Mississauga, Ontario)

as per manufacturer’s instructions and products were sequenced individually.

Overlapping segments of the pooled PCR products (maximum 600-bp in length) were

sequenced in the forward and reverse directions using the primers listed in Table 3.1. Sequences were

assembled and aligned using Clustal Omega - Multiple Sequence Alignment

(http://www.ebi.ac.uk/Tools/msa/clustalo/), screened for genetic variation and compared to genomic

95

sequences deposited in the Ensembl online genome browser database (Flicek et al. 2013).

Electrophoretograms were also manually examined for the presence of double (heterozygous) peaks.

PCR products in pooled groups that exhibited heterozygosity were then sequenced individually to

determine which sample(s) contained a polymorphic sequence. Polymorphisms were named based on

their nucleotide location relative to the first ATG start codon within the coding sequence and

annotated as described by the human genome variation society (den Dunnen and Antonarakis 2000).

Restriction Fragment Length Polymorphism Assays

Restriction fragment length polymorphism (RFLP) assays were developed using NEBcutter

V2.0 (Vincze et al. 2003) and used to screen additional pigs for the presence of the SFTPD SNPs

identified by sequencing. A smaller 365 bp segment of the promoter region, containing all three

newly-identified SNPs was amplified and subjected to RFLP analysis. The primers used in this PCR

reaction are shown in Table 3.1. PCR reactions (50 μL) were performed according to the

manufacturers recommendations using Platinum® Taq DNA polymerase (Invitrogen, Burlington,

Ontario) and a final primer concentration of 0.5 µM. Cycling parameters were as follows: initial

denaturation for 2 min at 94 ºC, followed by 34 cycles of denaturation at 94 ºC for 30 s, annealing at

54 ºC for 30 s and extension at 72 ºC for 30 s, with a final extension of 72 ºC for 5 min. Restriction

endonuclease enzymes (New England Biolabs, Whitby, ON, Canada) used for these studies and their

expected digestion patterns are summarized in Table 3.2. Restriction digestion with NspI, AciI and

EcoNI to detect SFTPD g.-4509A>G, SFTPD g.-4394G>A and SFTPD g.-4350C>T substitutions,

respectively, were performed on 3 L of PCR product using 5 units of enzyme and the incubation

conditions specified by the manufacturer. In all three reactions the enzyme digests the amplified PCR

product if the major or wild type allele is present. Fragments with evidence of heterozygosity were

individually sequenced to confirm the presence of the identified SNP (Lab Services Division,

University of Guelph, Guelph, Ontario).

96

Semi-Quantitative Real-Time RT-PCR

Variations in the constitutive expression of SFTPD and SCGB1A1 were also assessed using

semi-quantitative real-time RT-PCR. Following treatment with 7X gDNA wipeout buffer to eliminate

DNA contamination, RNA was reverse transcribed into cDNA using the QuantiTect® Reverse

Transcription Kit (QIAGEN, Mississauga, Ontario) as recommended by the manufacturer. Because

the lung is the primary site of expression of SFTPD and SCGB1A1, a standard curve was generated

for each primer set using serial five-fold dilutions of pooled porcine lung cDNA run in quintuplicate.

RT-PCR primers and reaction efficiencies for each standard curve are listed in Tables 3.3. PCR

products were sequenced to confirm amplification of the desired targets (Lab Services Division,

University of Guelph, Guelph, Ontario). Synthesized cDNA was analyzed in triplicate and PCR

reactions were performed on a Lightcycler® 480 system (Roche Applied Science, Salt Lake City,

Utah) according to the manufacturer’s recommendations (10 µl reaction volume) with primers at a

final concentrations of 0.5 µM. The fluorescence threshold value was calculated using Lightcycler®

480 system software. RT-PCR conditions were as follows: pre-incubation at 95 ºC for 5 min, followed

by 45 cycles of denaturation at 95 ºC for 10 s, annealing at appropriate gene melting temperature for

10 s (Table 3.3), and elongation at 72 ºC for 15 s, followed by melting curve analysis (65 to 95 ºC) to

confirm the presence of a single product per PCR reaction. RT-PCR product concentrations of

SCGB1A1 and STFPD relative to the reference gene GAPDH in each sample were determined and

calibrator normalized. Basal expression of SCGB1A1 and SFTPD was normalized based on GAPDH

mRNA expression (pooled liver cDNA at a 1:10x dilution was used to calibrate each 96-well plate).

The mean expression ratios (target gene: GAPDH expression) were determined using RelQuant

software from Roche Diagnostics (Laval, PQ, Canada).

The expression of GAPDH, 28s rRNA and 2M were analyzed as reference genes using the

RefFinder program (http://www. leonxie.com/referencegene.php); combining the BestKeeper (Pfaffl

et al. 2004), Normfinder (Andersen et al. 2004), Genorm (Vandesompele et al. 2002) and comparative

delta-Ct (Silver et al. 2006) methods. Using this program, GAPDH was found to be the most stable

reference gene in this data set and thus, was selected as the reference gene for evaluation of target

gene expression in this study.

97

The Mann-Whitney test was used to identify significant differences in microarray expression

between the two SFTPD g.-4509A>G SNP genotypes.

MALDI-TOF Mass Spectrometry Genotyping of Diseased and Healthy Pig Populations

Three groups of pigs were genotyped for the novel SFTPD SNPs: 1) diseased pigs of

unspecified breed (n = 386) submitted for autopsy evaluation to the Animal Health Laboratory (AHL),

University of Guelph; 2) healthy pure bred boars (n = 475), a reference population representing most

of the major North American breeds used in the commercial swine industry; and 3) healthy terminally

crossed market weight pigs of unspecified breed (n = 500). Pigs in the reference population of pure

bred boars were randomly selected and included Large White/Yorkshire (LW) 21.1 % (n = 100),

Landrace 21.1 % (n = 100), Hampshire 21.1 % (n = 100), Duroc 21.5 % (n = 102) and Pietrain 15.4 %

(n = 73) breeds. The selection of healthy market weight pigs was based on genetic heterogeneity as

determined in MALDI-TOF assays performed on all 21 previously identified innate immune gene

SNPs (Appendix I). To identify the production unit origin of each pig in this study, each pig’s tattoo

number was recorded at the time of collection. Pigs selected for MALDI-TOF genotyping,

represented a total of 140 unique production units and included the 96 pigs that had been previously

subjected to microarray expression analysis. The median number of pigs tested per production unit

was 3 (range 1 to 13).

Aliquots of DNA (10 to 40 ng/ μL; 40 to 200 μL) extracted from each pig were placed in 96-

well plates and submitted to the UHN Clinical Genomics Centre (Mount Sinai Hospital, Toronto,

Ontario). Genotyping was performed using Sequenom MassARRAY® matrix-assisted laser

desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (Sequenom, San Diego, CA,

USA) and single base extension (Gabriel et al. 2009). MassARRAY® Assay Design software was

used to design all of the multiplex assays. Allele-specific extension products were plated on a

SpectroChip and subjected to spectrometric analysis. Genotypes were identified by means of

SpectroCaller software and a manual review of all allele calls. Unfortunately, SNP genotyping for the

SFTPD g.-4394G>A and SFTPD g.-4350C>T polymorphisms failed and genotyping comparisons

98

could not be made for these variants. The identified SCGB1A1 polymorphisms were not available at

the time of SNP genotyping and genotyping comparisons could not be made for these variants.

For statistical analysis AHL pigs were grouped into broad disease syndrome groups

(infectious, enteric, pneumonia, polyserositis and septicemia) as determined by gross and histological

evaluation as performed by the board certified veterinary anatomic pathologists of the AHL.

Additionally, pigs were further grouped by pathogenic agent as diagnosed by bacterial culture, virus

isolation, PCR, ELISA and/or immunohistochemistry, performed by the AHL diagnostic laboratories.

Pathogenic agent groups included Actinobacillus pleuropneumoniae (APP) (n = 22); K88+

Escherichia coli (n = 31); Haemophilus parasuis (n = 20); Streptococcus suis (n = 84); Salmonella

enterica subsp. enterica ser. Typhimurium (Salmonella Typhimurium) (n = 26); Mycoplasma spp. (n

= 39); porcine circovirus type 2 (PCV2) (n = 84) and porcine reproductive and respiratory syndrome

virus (PRRSV) (n = 69). Variant genotype frequencies were then compared between the healthy

reference pig population (healthy market weight pigs) and the disease syndrome and pathogen groups.

Differences in the percent of animals possessing at least one variant allele between healthy

and diseased pig populations were then assessed by 2 x 2 contingency tables using one-tailed Fisher's

exact probability test analysis. Due to the multiple analyses performed on this data set (260) the false

discovery rate (FDR) was controlled by calculating q-values for each individual calculated p-value

using the FDRtool within the R stats package (Storey 2002, Storey 2003, Strimmer 2008). Analyses

with p-values < 0.05 and q-values < 0.03 were considered statistically significant when controlling the

FDR at 3 % (Storey 2002, Storey 2003, Strimmer 2008).

Variant genotype frequencies were also compared between pure bred pigs. A five-way Chi-

square test (five columns two rows) was used first to identify if any significant differences in variant

allele frequency existed or if the variant allele was considered to be equally distributed throughout all

populations. 2 x 2 contingency tables were then used to identify which specific breeds had a

significantly different variant positive genotype frequency when compared to the other breeds tested

99

in this study using a pairwise Yates Chi-square test or when the expected value for one or more of the

cells was < 5 a one-tailed Fisher's exact probability test was used instead.

Finally variant genotype frequencies within the healthy reference population were also

compared to that of four theoretical crossbred populations (50 % Duroc, 25 % Large White, 25 %

Landrace); (50 % Landrace, 25 % Large White, 25 % Duroc); (50 % Large White; 25 % Landrace, 25

% Duroc) and (33 % Large White, 33 % Landrace, 33 % Duroc) where the variant genotype

frequency was calculated using the proposed percentage that each breed would contribute to the cross

and the measured variant genotype frequency of each purebred population.

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Table 3.1. Primers used for promoter region amplification, sequencing and RFLP assays of SCGB1A1 and SFTPD.

PCR reaction Ensembl ID Primer name Nucleotide sequence (5' > 3') Amplicon

length (bp)

SCGB1A1 promoter amplification [ENSSSCT00000030155] SCGB-1988 FWD GCTTGTTTCTGTGCCTTG 2362

SCGB 355 REV CTCGTGACTCCCATCCTGTT

SCGB1A1 promoter sequencing [ENSSSCT00000030155] SCGB-1585REV GCTGGGAGTTGGCTGAGATA N/A

SCGBlf-1666FWD GCGCCACAATGGGAACTC N/A

SCGB-1007REV ACTCCTGTTCTTTCCTGTTT N/A

SCGB-1026FWD AAACAGGAAAGAACAGGAGT N/A

SCGB-318REV GAAGCAACTGTCAATCCTATCTGG N/A

SCGB 355REV CTCGTGACTCCCATCCTGTT N/A

SFTPD promoter amplification [ENSSSCT00000034629] SPD-5328FWD CCATCAGACAAACCACAAGCAC 2682

[ENSSSCT00000011312] SPD-2665REV CACCTCCAACACCCACCCT

SFTPD promoter sequencing [ENSSSCT00000034629] SPD-5328FWD CCATCAGACAAACCACAAGCAC N/A

[ENSSSCT00000011312] SPD-4049REV ATTCTTATTTAGGATGACCC N/A

SPD-4203FWD CTTGGTGGAATGTGGAGTTAG N/A

SPD-2893REV GCAAGACCAGAAACACTCAC N/A

SFTPD RFLP analysis [ENSSSCT00000034629] SPD-4585FWD GCTAATGAAATCCACCAGG 365

[ENSSSCT00000011312] SPD-4239REV ATCCAACCCAGACACTCAT

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Table 3.2. Restriction endonucleases used in RFLP assays to genotype pigs for SFTPD promoter polymorphisms.

Genotype Restriction endonuclease Recognition site Genotype Expected fragment lengths

(bp)

SFTPD g.-4350C>T EcoNI CCTNN/NNNAGG

CC

CT

TT

128, 237

128, 237, 365

365

SFTPD g.-4394G>A AciI C/CGC

GG

GA

AA

173, 192

173, 192, 365

365

SFTPD g.-4509A>G NspI RCATG/Y

AA

AG

GG

79, 286

79, 286, 365

365

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Table 3.3. Primers used for semi-quantitative real-time RT-PCR for SCBG1A1 and SFTPD.

Gene Ensembl ID Forward Primer (5' > 3') Reverse Primer (5' > 3')

Melting

temperature

(ºC)

Amplicon

length

(bp)

PCR

efficiency

SCGB1A1 [ENSSSCT00000030155] CCAGTTACCAGGCTTCAGTT GTCTTCAGGTTCCAAATCC 54 176 1.99

SFTPD [ENSSSCT00000034629]

[ENSSSCT00000011312] GCTTCTCCTCCCTCTCTCCG GCATCCCCGCTCGCCCTACA 62 230 1.95

B2M [ENSSSCT00000005170] TCTACCTTCTGGTCCACACTGAG TCATCCAACCCAGATGCA 60 161 1.90

GAPDH [ENSSSCT00000000756] GAAGGCTGGGGCTCACTT GTCTTCTGGGTGGCAGTGAT 60 227 2.08

28S [ENSSSCT00000006752] CGGGTAAACGGCGGGAGTAA TAGGTAGGGACAGTGGGAAT 60 294 1.83

103

RESULTS

Novel SNPs and Polymorphisms in the 5'-Promoter Regions of SCGB1A1 and SFTPD

Three different gel patterns were observed for the amplified 5'-promoter region of SCGB1A1

(Figure 3.1; only data of the eight pigs with the lowest and highest levels of SCGB1A1 expression is

shown). PCR products amplified from the eight pigs with the lowest levels of SCGB1A1 expression,

as determined by microarray analysis, contained a single fragment that was ~2362 bp in length and

was near identical to the sequence reported in the Ensembl online genome browser database

[ENSSSCT00000030155] (Flicek et al. 2013). A novel single transition SNP, g.-748G>A, was

detected in the pooled sample containing the second lowest group of four pigs. Seven of eleven (63.6

%) pigs with the highest level of SCGB1A1 expression contained this same fragment in addition to a

PCR product that was approximately 333-bp longer (2695-bp). The remaining 4 pigs (36.4 %), those

with the first, second, fourth and eleventh highest SCGB1A1 expression levels, contained only the

larger 2695-bp fragment (Figure 3.1). Recently, a second porcine SCGB1A1 sequence was annotated

in the Ensembl website database. This sequence appears to be a separate second gene located 44,396

bp upstream on the reverse strand of the same chromosome, Sus scrofa chromosome 2

[ENSSSCT00000014276] (Figure 3.2) (Flicek et al. 2013). Comparison of the 2363-bp sequence

generated from the 8 pigs with lowest levels of SCGB1A1 expression to the reference sequence of the

second reported SCGB1A1 gene sequence ([ENSSSCT00000014276]) resulted in the identification of

29 SNPs (23 transition and 6 transversion SNPs), two insertions and three deletions within the 1903

bp of the 5'-upstream (promoter) region; two transition SNPs within the UTR of exon 1 and three

SNPs (two transition and one transversion SNP) within the first 234 bp of intron1-2 within this new

reference sequence (Appendix IV - Figure V.1). The sequence of the larger fragment amplified from

pigs with high levels of SCGB1A1 mRNA expression was nearly identical to the newly identified

second gene reported in the Ensembl website database ([ENSSSCT00000014276]) and apart from the

g.-748G>A SNP, contained all the aforementioned identified variations. In addition to the numerous

variations present when compared to the shorter 2,362-bp fragment, the 2,695-bp sequence had an

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additional transition SNP within exon 1 (g.-9C>T). Please see Table 3.4 and Appendix IV – Figure

IV.1 for a summary of all identified variations.

Three novel transition SNPs were identified within the 2682 bp fragment amplified from the

5'-upstream promoter region of SFTPD: SFTPD g.-4509A>G; SFTPD g.-4394G>A and SFTPD g.-

4350C>T (Appendix IV – Figure IV.2).

The top 15 and bottom 15 expressing pigs were genotyped for the three newly identified

SFTPD SNPs using the designed RFLP assay (Figure 3.4). Six of seven pigs (85.7 %) with the highest

SFTPD expression, as measured by microarray technology, were heterozygous for at least one of the

three newly identified SNPs. All of the remaining pigs subjected to RFLP genotyping (n = 23) were

homozygous wild type at all three alleles (Figure 3.5). None of the pigs were homozygous for any of

the variant alleles. Based on these initial 30 animals, the SFTPD g.-4509A>G and SFTPD g.-

4394G>A SNPs appeared to be linked, with the G at position -4509 always occurring with the A at

position -4394. Based on MALDI-TOF mass spectrometry SNP genotyping, all remaining pigs in this

data group (n = 85) were homozygous wild type for the SFTPD g.-4509A>G SNP. MALDI-TOF

mass spectrometry SNP genotyping was 100 % in agreement with the RFLP assay for this SNP.

Animals that were heterozygous (n = 3) for the SFTPD g.-4509A>G SNP showed a significant

increase in hepatic expression of SFTPD when compared to the wild type allele (AA) (n = 85) (p =

0.0054) (Figure 3.6 and Table 3.5).

The SFTPD g.-4509A>G SNP was not found to be statistically more frequent in any of the

different disease syndrome, bacterial and viral pathogen groups as compared to the healthy reference

pig population after controlling the FDR (3 %) (Table 3.6). The G allele of the SFTPD g.-4509A>G

SNP was however increased two- to four- fold in those pigs that were infected with a variety of

pathogens associated with pulmonary infections and pneumonia including H. parasuis, Mycoplasma

spp., PCV2 and PRRSV (Table 3.6).

The SFTPD g.-4509A>G SNP was represented in all examined North American breeds,

however was quite rare throughout most genotyped populations. The percentage of animals with at

least one variant allele ranged from 1.2 to 5.0 % with the exception of the Hampshire (28.3 %) and

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Large White (8.0 %) breeds both of which were significantly different from other purebred pig breeds

(Table 3.7, Table 3.8, Table 3.9 and Figure 3.7). Only three (0.2 %) of the pigs genotyped (n = 1361)

pigs genotyped were homozygous for this SNP.

Correlation between SCGB1A1 and SFTPD mRNA Expression Levels

SCGB1A1 mRNA expression varied widely among different pigs. After excluding a single

high expressing outlier, a gene expression ratio was calculated by comparing the mean expression

values of the top 50 % of pigs to the bottom 6 % of pigs which resulted in a GER of 202 when

measured by RT-PCR and a 245 when assessed by microarray technology. The maximum variation

between the pig with the highest and lowest RT-PCR levels was 1430-fold compared to 1242-fold

when measured by microarray expression. There was a strong positive correlation between the

expression levels detected by the microarray and RT-PCR methods (R2 = 0.7237) (Figure 3.3).

Amplification of SFTPD from liver cDNA was not consistent. Crossing points often exceeded 35

cycles and relative quantification of hepatic SFTPD mRNA could not be evaluated.

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Table 3.4. Identified SCGB1A1 sequence variations.

Annotation Description Location

SCGB1A1 g.-1885-1887delTGT Deletion (3 bp) Promoter

SCGB1A1 g.-1863T>C Transition SNP Promoter

SCGB1A1 g.-1842C>T Transition SNP Promoter



SCGB1A1 g.-1761G>C Transversion SNP Promoter


SCGB1A1 g.-1730T>G Transversion SNP Promoter


SCGB1A1 g.-1708G>A Transition SNP Promoter

SCGB1A1 g.-1703A>G Transition SNP Promoter








SCGB1A1 g.-1050-1051ins

GGAGTTCCCGTCGTGGCGCAGTGGTTAACGAATCCGACTAGGAACCATGA

GGTTGCGGGTTCGATCCCTGCCCTTGCTCAGTGGGTTAACGATCCGGCGTT

GCCGTGAGCTGTGGTGTAGGTTGCAGACGCGGCTCGGATCCTGCGTTGCTG

TGGCTCTGGCATAGGCCGGTGGCTACAGCTCCGATTCAACCCCTAGCCTGG

GAACCTCCATATGCCGCGGAAGCGGCCCAAGAAATAGCAACCATAACAAC

AACAACAACAACAAAAAAAAAAAAGACAAAAGACAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGAATCAAAGTCT

Insertion (344 bp) Promoter

* indicates SNPs only identified in the shorter sequenced SCGB1A1 promoter fragment. All remaining genetic variations were identified in the longer

sequenced promoter fragment. Nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000).

107

Table 3.4: continued.


SCGB1A1 g.-1000A>C>G Transversion SNP Promoter


SCGB1A1 g.-925-926insGTG Insertion (3 bp) Promoter





SCGB1A1 g.-748G>A*

Transition SNP Promoter

SCGB1A1 g.-774-783delACAAAAAACA Deletion (10 bp) Promoter

SCGB1A1 g.-620delA Deletion (1 bp) Promoter




SCGB1A1 g.-363T>A Transversion SNP Promoter



SCGB1A1 g.-73A>G Transition SNP Exon 1 UTR

SCGB1A1 g.-68A>G Transition SNP Exon 1 UTR

SCGB1A1 g.-9C>T

Transition SNP Exon 1 UTR

SCGB1A1 g.87IVS1C>T Transition SNP Intron 1-2

SCGB1A1 g.230IVS1T>A Transversion SNP Intron 1-2

SCGB1A1 g.266IVS1C>T Transition SNP Intron 1-2

* indicates SNPs only identified in the shorter sequenced SCGB1A1 promoter fragment. All remaining genetic variations were identified in the longer

sequenced promoter fragment. Nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000).

108

Figure 3.1. SCGB1A1 promoter amplification of top and bottom eight expressing pigs.

A single smaller fragment (2,362 bp) was amplified in the eight pigs with the lowest microarray expression. Seven of eleven (63.6 %) pigs with the highest

level of SCGB1A1 expression contained this same fragment in addition to a PCR product that was approximately 333-bp longer (2,695-bp). The remaining 4

pigs (36.4 %), those with the first, second, fourth and eleventh highest SCGB1A1 expression levels, contained only the larger 2,693-bp fragment. Only results

of the top and bottom eight pigs are shown. Gel electrophoresis on a 2 % agarose gel in 0.5 X TBE buffer with 1 X SYBR SAFE nucleic acid stain.

109

Figure 3.2. Regional Ensembl annotation of Sus scrofa chromosome number 2.

Two SCGB1A1 genes, located 44,396 bp apart on the same chromosome, are annotated within the porcine genome. SCGB1A1.2-201

[ENSSSCT00000030155] is located on Sus scrofa chromosome 2, spanning from nucleotide 8,570,774 to 8,575,570 on the forward strand. SCGB1A1.1-201

[ENSSSCT00000014276] is also located on Sus scrofa chromosome 2, spanning from nucleotides 8,619,966 to 8,624,573. (Flicek et al. 2013).

110

Figure 3.3. Correlation between SCGB1A1 mRNA expression as measured by semi-quantitative real-time RT-PCR and microarray.

R2 = Correlation coefficient.

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Figure 3.4. Restriction length fragment polymorphism analyses developed to genotype pigs for the three identified SFTPD promoter SNPs.

A 365 bp segment of the promoter region, containing all three newly-identified SNPs was amplified and subjected to RFLP analysis using the following

endonucleases: EcoNI for SFTPD g.-4350C>T (left); AciI for SFTPD g.-4394G>A SNP (middle); and NspI for SFTPD g.-4509A>G SNP (right). All

reactions were designed to digest the major or wild type allele and none of the pigs tested were homozygous for any of the variant alleles. Gel electrophoresis

on a 2 % agarose gel in 0.5 X TBE buffer with 1 X SYBR SAFE nucleic acid stain.

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Figure 3.5. Microarray expression of SFTPD.

A distinct subpopulation with enhanced mRNA expression is observed. Six out of the seven individuals (85.7 %) with the highest expression contain at least

one of the identified SNPs. Individuals that contained the SFTPD g.-4350C>T SNP are indicated in red. The SFTPD g.-4509A>G and SFTPD g.-4394G>A

SNPs always occurred together suggesting that these variants were 100 % linked and are indicated in orange. Each diamond represents an individual pig’s

expression value relative to the microarray expression of GAPDH. Pigs not tested are indicated in blue however MALDI-TOF mass spectrometry SNP

genotyping indicated that all remaining pigs were homozygous wild type for the SFTPD g.-4509A>G SNP.

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Table 3.5. Effect of the SFTPD g.-4509A>G SNP on hepatic gene expression.

Relationship between mean relative hepatic expression of SFTPD and the identified SFTPD g.-4509A>G promoter SNP. Mean gene expression was

calculated using microarray expression relative to that of the housekeeping gene GAPDH.

Genotype AA AG GG

Mean

expression

Standard

deviation n =

Mean

expression

Standard

deviation n =

Mean

expression

Standard

deviation n =

SFTPD g.-4509A>G 2.0547 4.2258 85 17.8748 8.163 3 N/A N/A 0

Figure 3.6. Hepatic expression of SFTPD in SFTPD g.-4509A>G SNP genotypes.

Relationship between mean relative hepatic expression of SFTPD and the two SFTPD g.-4509A>G SNP genotypes. Animals that were heterozygous (n = 3)

for the SFTPD g.-4509A>G SNP showed a significant increase in hepatic expression when compared to the wild type allele (n = 85) (p = 0.0054). No

homozygous individuals were identified in this subset of pigs. * indicates a significant difference at p < 0.05.

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Table 3.6. Frequency of variant positive genotypes for the SFTPD g.-4509A>G SNP in pigs

diagnosed with different disease syndromes, bacterial and viral pathogens.

Comparison of the percentage of animals with at least one variant allele between the healthy reference

population and different disease groups as well as bacterial and viral pathogen groups. No statistically

significant frequency variations are observed (p < 0.05; FDR < 0.03). 1,2,3 etc. represent number of

animals with a miss call for that SNP in that group (e.g. in the infectious disease group, the SFTPD g.-

4509A>G had 1 miscall meaning the number of data points is = 358 −1 or 357).

SFTPD g.-4509A>G Variant

positive (%) p-value q-value

Healthy market pigs (n = 500) 1.2 N/A N/A

Infectious disease (n = 358) 1.11

0.5914 0.0762

Enteric disease (n = 182) 1.11

0.6391 0.0932

Pneumonia (n = 244) 1.21

0.6083 0.0817

Polyserositis (n = 56) 1.8 0.5264 0.0862

Septicemia (n = 92) 1.1 0.7016 0.1238

APP (n = 22) 0 0.7713 0.2174

K88+ E. coli (n = 31) 0 0.6958 0.1746

Haemophilus parasuis (n = 20) 5 0.2413 0.0603

Streptococcus suis (n = 84) 0 0.3922 0.0579

Salmonella Typhimurium (n = 26) 0 0.7366 0.1715

Mycoplasma spp. (n = 39) 2.6 0.4107 0.1042

PCV2 (n = 84) 2.41

0.3186 0.0521

PRRSV (n = 69) 2.91

0.2467 0.0588

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Table 3.7. Frequency of variant positive genotypes for the SFTPD g.-4509A>G promoter SNP in purebred pigs.

Comparison of the percentage of animals with at least one variant allele between purebred pig breeds. 1 represent number of animals with a miss call for that

SNP in that group (e.g. in the Hampshire group, the SFTPD g.-4509A>G had 1 miscall meaning the number of data points is = 100 − 1 or 99). * Difference in

% variant positive compared between all breeds using a Chi-square test (five columns two rows). Bolded text indicates a significant difference at p < 0.05.

Genotype Duroc

(n = 102)

Hampshire

(n = 100)

Landrace

(n = 100)

Large White

(n = 100)

Pietrain

(n = 73) p-value

*

SFTPD g.-4509A>G 3.9 28.31

3 8 1.4

< 0.0001

Table 3.8. p-values for pair-wise comparisons of SFTPD g.-4509A>G SNP variant genotype frequencies in purebred pigs.

The p-values indicate the statistical significance between the comparison of the percentage of animals with at least one variant allele between different

purebred pig breeds as assessed using a Yates chi-square test. * indicates analyses where a one-tailed Fisher's exact probability test was used instead of the

chi-square test. Bolded text indicates a significant difference at p < 0.05.

SFTPD g.-4509A>G Duroc Hampshire Landrace Large White Pietrain

Duroc N/A < 0.0001 0.5110* 0.3537 0.3048*

Hampshire N/A < 0.0001 0.0004 < 0.0001

Landrace N/A 0.2146 0.4363*

Large White N/A 0.0500*

Pietrain N/A

Table 3.9. Frequency of variant positive genotypes for the SFTPD g.-4509A>G promoter SNP in weighted cross bred pig populations.

Comparison of the percentage of animals with at least one variant allele between the healthy reference population and different weighted cross bred pig

populations. LW = Large white

Genotype

Healthy

market pigs

(n = 500)

50 % Duroc

25 % LW

25 % Landrace

50 % Landrace

25 % LW

25 % Duroc

50 % LW

25 % Landrace

25 % Duroc

33 % LW

33 % Landrace

33 % Duroc

SFTPD g.-4509A>G 1.2 4.7 4.5 5.7 4.9

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Figure 3.7. Frequency of variant positive genotypes for the SFTPD g.-4509A>G SNP in healthy

pure bred and cross bred pigs.

A: Comparison of the percentage of animals with at least one variant allele between purebred pig

populations.

B: Comparison of the percentage of animals with at least one variant allele between the healthy

crossbred reference population and different weighted cross bred pig populations.

LW = Large White; LR = Landrace

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DISCUSSION

To our knowledge, this is the first study to identify SNPs within the 5'-promoter region of the

porcine SFTPD and SCGB1A1 genes and apart from the additionally annotated SCGB1A1 gene in the

ensemble database is also the first to report a potential second copy of the porcine SCGB1A1 gene.

Each of these newly identified polymorphisms was present in a subset of healthy pigs and, when

present, was associated with increased levels of mRNA expression.

The C-type lectin group of receptors has been previously linked to infectious disease

susceptibility in both humans and pigs (Hallman and Haataja 2006, Keirstead et al. 2011, Lillie et al.

2007, Pastva et al. 2007, Sorensen et al. 2007). Four SNPs in the promoter region of MBL2 (-2148 (T

to C), -1081 (G to A), -1636 (T to G), and -1614 (A to G) have been detected at increased frequencies

in pigs diagnosed with infectious diseases (Keirstead et al. 2011, Lillie et al. 2007). A number of

SNPs have also been previously identified in the coding regions of the surfactant pulmonary-

associated protein A (SFTPA or SP-A) gene of pigs (Keirstead et al. 2011). One of these SNPs,

T(599)A, was found to be more frequent in pigs diagnosed with various infectious diseases (Keirstead

et al. 2011). Several SNPs have also been reported in the collagen-like domain of the human SP-A

and SP-D genes, some of which are associated with impaired pulmonary defence, increased

susceptibility to infectious diseases and reduced serum levels of SP-D (Crouch et al. 1993, DiAngelo

et al. 1999, Hallman and Haataja 2006, Heidinger et al. 2005, King and Kingma 2011, Lahti et al.

2002, Pastva et al. 2007, Sorensen et al. 2006, Sorensen et al. 2007). Other studies have shown that, as

reported for MBL-A in pigs (Juul-Madsen et al. 2006)), serum levels of SP-D are a genetically

acquired trait with a heritability of approximately 0.83 in adults and 0.91 in children (Husby et al.

2002, Sorensen et al. 2006). One specific polymorphism and its associated haplotypes, 11 (Met/Thr)

has been shown to account for ~50 % of the observed variation in serum levels of SP-D (Leth-Larsen

et al. 2005, Sorensen et al. 2006).

Our results suggest that the presences of these genetic variations in SFTPD and SCGB1A1 are

associated with enhanced, rather than decreased gene expression in contrast to that previously shown

with MBL2 promoter polymorphisms. Given the important role that pigs play as vectors of potential

118

zoonotic and anthropo-zoonotic diseases, it will be particularly important to determine whether

elevated pre-immune levels of SP-D especially in the respiratory tract are protective against diseases

such as influenza-A viruses (IAV) and Mycobacterium tuberculosis. A number of studies have shown

that SP-D plays a critical role in macrophage activation and in the opsonisation and agglutination of

IAV, including swine, avian and human influenza viruses (Hartshorn et al. 1994, Hartshorn et al.

1997, Hartshorn et al. 2000, Hawgood et al. 2004, Hillaire et al. 2011, Hillaire et al. 2012, Hillaire et

al. 2013, LeVine et al. 2001, van Eijk et al. 2012). Unlike other mammalian SP-Ds, porcine SP-D

contains a unique N-linked sialic acid-rich glycan in its CRD that interacts with conserved sialic acid

receptors on the surface of IAV (Hillaire et al. 2011, Hillaire et al. 2013, van Eijk et al. 2012). As a

result, porcine SP-D serves as a decoy receptor that competes with virus binding to the respiratory

epithelium. Porcine SP-D therefore not only represents an important effector in the defense against

infection with economically important diseases such as swine influenza but may also play a crucial

role to ward off infection with pandemic human, avian and porcine influenza viruses. The importance

of this critical function of porcine SP-D is further underscored by the potential of developing a

recombinant form to be used for future therapeutic applications (Hillaire et al. 2011, Hillaire et al.

2013, van Eijk et al. 2012). SP-D also limits macrophage uptake of Mycobacterium tuberculosis

through agglutination-dependent and -independent mechanisms (Ferguson et al. 2002). Genetic

variations that may lead to enhanced expression of SFTPD, such as those identified in this study, may

in theory afford a protective phenotype to these specific diseases in pigs.

In the current study no significant variation in positive genotype frequencies were identified

for the SFTPD g.-4509A>G SNP in pigs of the various disease and pathogen groups. This lack of

statistical significance is in part due to the relative scarcity of this SNP within the assessed healthy

and diseased populations. A protective effect associated with the presence of this SNP was not

observed and in fact the positive variant genotype frequency was increased in pigs, though not

significantly so, of a variety of pathogens groups associated with pulmonary infections and

pneumonia. Studies in SFTPD-/-

mice challenged with intraperitoneal injection of lipopolysaccharide

(LPS) also suggests that SP-D plays a regulatory role in the lung by inhibiting pulmonary

119

inflammation and migration of peripheral monocytes into the lung through GM-CSF–dependent

pathways (King and Kingma 2011). It should therefore also be considered that excessive activation of

macrophages, by increased levels of SP-D can in fact be detrimental if it results in persistent or

excessive inflammation and tissue damage. Additionally gene expression may vary between different

tissues depending on the existence of tissue specific transcription factors and therefore the effect of

promoter polymorphisms on gene expression may be affected by the presence of such tissue specific

transcription factors. Both the NFAT (nuclear factor of activated T cells) family and TTF-1 (thyroid

transcription factor 1) are transcription factors that have been shown to be important in the regulation

of pulmonary expression of SFTPD in mice (Dave et al. 2004) and both have also been shown to have

tissue specific distributions (Civitareale et al. 1989, Guazzi et al. 1990, Rao et al. 1997). Likewise this

tissue specific distribution may also be true for other transcription factors that may be involved in

regulation of SFTPD expression in pigs and it should be established if the promoter polymorphisms

identified in this study would affect tissue specific transcription factor binding of NFAT, TTF-1 and

other transcription factors in the lung of pigs.

The low genotype frequency and relative increased frequency with pulmonary pathogen

infections, although not statistically significant, may in fact suggest that increased levels of SP-D may

be detrimental to innate host defenses. Very few homozygous individuals were identified in this study

and it is not clear if this can be expected based on the low allele frequency or whether or not

homozygosity results in a distinct disadvantage and lethality. Additional surveys of larger samples of

animals with respiratory diseases will be especially helpful to further evaluate this possibility. The

SFTPD g.-4509A>G SNP genotype frequency also varied between different breeds of purebred boars,

although still relatively rare in all but the Large White and especially Hampshire breeds which had a

much higher genotype frequency.

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Previous studies of the porcine genome suggested that it contained only a single copy of the

SCGB1A1 gene (Gutierrez Sagal and Nieto 1998). This is similar to most species, including humans,

rabbits, rats, mice and primates who also only contain a single copy of the SCGB1A1 gene. In

contrast, horses contain three copies of this gene, presumably due to an intrachromosomal gene

triplication (Cote et al. 2012). These consist of SCGB1A1 and SCGB1A1A, which code for two similar

proteins that have proposed differences in function; and SCGB1A1P, which contains a nonsense

mutation and is not expressed. As reported in our study, it now appears that there may be a second

porcine SCGB1A1 gene that contains a large 334 bp insertion along with multiple other promoter

polymorphisms when compared to the previously reported SCGB1A1 gene sequence. An extra PCR

product of higher molecular weight was amplified in a subset of eleven pigs that expressed the highest

levels of SCGB1A1 mRNA. Although not reported in the literature, a search of the Ensemble website

indicated that an additional SCGB1A1 sequence had recently been annotated in the database as a

separate gene located 44 396 bp upstream on the reverse strand of Sus scrofa chromosome 2

[ENSSSCT00000014276] (Figure 3.2) (Flicek et al. 2013). Further analysis indicated that the long

promoter sequences detected in pigs with higher mRNA expression were near identical to each other

as well as to the newly deposited sequence in the Ensemble database. This sequence contained a large

number of genetic variations that were not present in the short promoter form of the gene. Most of

these variations were present in non-coding regions of the gene. Only three nucleotide variations were

observed in exon 1, with all three located 5' of the ATG start codon. Although our initial data supports

the existence of two unique SCBG1A1 genes, additional studies are required to further verify that

these sequences represent separate genes rather than extensive variation within a single gene.

Additional studies will also be needed to determine the biological and functional significance of the

two different SCBG1A1 sequences and also whether or not any sequence variation exists between the

coding regions of these two genes.

In humans SCGB1A1 is expressed at high levels in a broad range of tissues (lung, uterus,

trachea, prostate, thyroid, mammary gland and pituitary (Peri et al. 1993) with lower levels of

expression being detected in the stomach, ovary, testis, spleen, adrenal, aorta, pancreas, thymus and

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liver (Peri et al. 1993) with similar tissue variation in horses (Cote et al. 2012). Expression of

SCGB1A1 mRNA has also been detected in high levels in the lung, but not in the liver of pigs using

northern blot analysis (Gutierrez Sagal and Nieto 1998), a technology that is considered less sensitive

than the microarray and RT-PCR assays used in our study. In our study, there was a strong correlation

in hepatic mRNA levels measured by these two independent methods. Expression in both cases

should be viewed as total mRNA expression of both the long and short promoter forms of SCGB1A1

as neither RT-PCR primers nor the microarray probe used in this study were capable of discerning

between these two reported sequences. In this study, the polymorphic longer sequence was identified

only in pigs with the highest measured SCGB1A1 expression suggesting an association between this

polymorphic sequence and enhanced hepatic expression of this gene. Variations in the SCGB1A1 gene

that are associated with specific disease syndromes have also been identified. A G(38)A SNP [also

known as G(-26)A] in humans has been linked to increased airway inflammation, acute respiratory

distress syndrome and the development of asthma (Candelaria et al. 2005, Choi et al. 2000, Frerking

et al. 2005, Ku et al. 2011, Laing et al. 1998, Zhang et al. 1997). Additionally, alterations in the

expression ratio of SCGB1A1A to SCGB1A1 in horses are associated with recurrent airway

obstruction syndrome (RAO) (Cote et al. 2012). Differences in the amount of this secretory protein in

healthy pigs, such as that observed for the polymorphic sequence in this study, can therefore also be

expected to have a significant effect on an animal’s susceptibility and response to allergens and

infectious pathogens. Accordingly, it would be interesting to determine if there are other promoter

polymorphisms in SCGB1A1 not apparent in liver expression studies that affect pulmonary resistance

to respiratory pathogens in pigs or other species.

This study represents an important first step in the identification of innate immune genes that

are differentially up-regulated in the liver of healthy pigs and thus, may serve as markers of enhanced

pre-immune resistance to pulmonary (and other) infectious diseases. Both genes code for innate

immune response proteins that play a key role in host defense against infectious pathogens, especially

in the lung and additional studies will be required to determine if these findings can be extrapolated to

the lung and other tissues. It should also be established whether higher levels of mRNA expression

122

translates into increased levels of functional protein. Such studies would require the measurement of

pulmonary gene expression as well as protein levels in lung and/or serum. Additional investigations

may be aimed at genotyping larger populations in conjunction with controlled prospective infection

trials and carefully designed disease association studies to further evaluated the importance of these

promoter SNPs on innate immune defenses and determine whether they offer a protective advantage

or disadvantage in different pig populations. Genetic variations in these genes may represent a

valuable set of biomarkers that can be used to examine the relationship between innate immunity and

disease resistance and to develop a comprehensive selection panel of markers for breeding pigs with

increased disease resistance.

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CHAPTER 4: VARIATION IN CONSTITUTIVE HEPATIC GENE EXPRESSION OF HAMP

AND DDX58 WITH IDENTIFICATION OF NOVEL PROMOTER POLYMORPHISMS


authorship:

Snyman HN, Hammermueller JD, Hayes MA, Lillie BN (2013)

ABSTRACT

Single nucleotide polymorphisms (SNPs) within the porcine innate immune genome have

been associated with alterations in gene expression and an increased risk to developing infectious

diseases. In a recent study, a number of additional porcine innate immune genes with widely variable

constitutive gene expression were identified. To evaluate if promoter polymorphisms are responsible

for the observed variation, we attempted to characterize the 5' upstream promoter regions of four of

these genes that exhibited some of the highest variation; including porcine hepcidin antimicrobial

peptide (HAMP), retinoic acid-inducible gene 1 (DDX58), peptidoglycan recognition protein-1

(PGLYRP1) and peptidoglycan recognition protein-2 (PGLYRP2). Pooled sequencing of these genes

in the lowest and highest expressing animals resulted in the identification of fourteen and nineteen

novel polymorphisms within the 5'-upstream promoter of the HAMP and DDX58 genes respectively,

while no polymorphisms were identified in the genes encoding PGLYRP1 and PGLYRP2. Some

polymorphisms identified in the HAMP and DDX58 genes were more frequent in pigs with either

increased or decreased mRNA expression. A significant increase or decrease in variant genotype

frequency in pigs diagnosed with a variety of common disease syndromes and pathogens was

identified for several of these HAMP and DDX58 promoter polymorphisms as well as some CD163

and CD169 coding SNPs. These polymorphisms could serve as genetic markers aimed at enhancing

innate resistance to common infectious diseases encountered by swine.

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INTRODUCTION

The innate immune system is a critical component of the host immune response and

represents the first line of defense to invading pathogens (Janeway 1989, Medzhitov 2009, Mogensen

2009). This system is composed of an elaborate network of interacting pattern recognition receptors

(PRRs) and secreted proteins that can rapidly identify, neutralize and/or eliminate bacterial, fungal

and viral pathogens.

A large group of secreted innate immune response proteins are the antimicrobial peptides

(AMPs), also known as host defense peptides (HDPs). AMPs are a highly heterogeneous group of

proteins that have the ability to rapidly inactivate microbial organisms including Gram-positive and

Gram-negative bacteria, fungi and certain viruses (Auvynet and Rosenstein 2009, Sang and Blecha

2009, Zaiou and Gallo 2002). Cathelicidins and defensins are the major mammalian AMPs. However,

a number of cysteine stabilized peptides with antibacterial activity have also been identified, including

the liver expressed antimicrobial peptides (Hepcidin/LEAP-1 and LEAP-2), peptidoglycan

recognition proteins (PGLYRPs) and NK-lysin (Dziarski and Gupta 2010, Sang and Blecha 2009).

LEAP-1, better known as hepcidin antimicrobial peptide plays an important role in iron metabolism

(Krause et al. 2000, Sang et al. 2006). However, as its the name suggests, HAMP also has important

antimicrobial activities (Barthe et al. 2011, Hocquellet et al. 2012, Krause et al. 2000, Park et al. 2001,

Sang et al. 2006). Four PGLYRPs have been identified in mammals with these proteins sharing some

homology to the previously identified insect PGRPs. Mammalian PGLYRPs contain one or more C-

terminal type 2 amidase domains with a peptidoglycan-binding groove cleft that is specific for

muramyl-tripeptide (Guan et al. 2004, Liu et al. 2001, Royet and Dziarski 2007). All mammalian

PGLYPRs exist as secreted proteins with PGLYRP1, PGLYRP3, and PGLYRP4 forming disulfide-

linked homodimers. Homodimerization of PGLYRP2 also occurs but is independent of disulphide

bond formation (Dziarski and Gupta 2010). PGLYRP3 and PGLYRP4 can also form disulfide-linked

heterodimers (Dziarski and Gupta 2010).

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In addition to AMPs, PRRs also play a central role in the innate immune defenses against

microbial pathogens. An important group of intracytoplasmic PRRs are the retinoic acid-inducible

genes (RIG)-I–like receptors (RLR’s). RLRs play a critical role in antiviral sensing and signaling

pathways (Kato et al. 2006, Saito et al. 2007, Schlee et al. 2009, Takeuchi and Akira 2010, Wilkins

and Gale 2010, Yoneyama et al. 2005). They are IFN-inducible RNA helicases that recognize foreign

cytoplasmic RNA and DNA. This innate defense mechanism is particularly important in the case of

viral pathogens that have breached the cytoplasmic compartment of an infected host cell and are

actively replicating and producing mRNA for protein synthesis. A number of molecules have been

added to this class of PRRs but the RIG-1 and melanoma-differentiation-associated gene 5 (MDA-5;

also known as interferon-induced helicase/IFIH1 or helicard, encoded by the IFIH1 gene) proteins are

the prototypical members of this group. These proteins recognize a broad range of RNA viruses (Kato

et al. 2006, Wilkins and Gale 2010, Yoneyama et al. 2005). After binding to their cognate ligands, the

N-terminal caspase recruitment domain (CARD) of RIG-1 and MDA-5 trigger intracellular signaling

pathways via the IFN-β promoter stimulator-1 (IPS-1 also known as MAVS, VISA or CARDIF). This

promotes type 1-IFN production via tumour necrosis factor (TNF) receptor-associated factor 3

(TRAF3) and TNF receptor type 1-associated DEATH domain protein (TRADD) (Michallet et al.

2008) as well as IκB kinase (IKK-I and Tank binding kinase1/TBK1) signalling pathways (Akira et

al. 2006, Honda et al. 2006). Activation of RIG-1 by the short dsRNA and 5'-triphosphate dsRNA

found in RNA and DNA viruses enhances type I-IFN signaling (Schlee et al. 2009, Schmidt et al.

2009).

Alterations in the expression of innate immune proteins as a result of underlying genetic

variations, in both humans and pigs, has been shown to significantly alter the susceptibility of

individuals to infectious disease (Garred et al. 2003, Juul-Madsen et al. 2006, Juul-Madsen et al.

2011, Keirstead et al. 2011, Leth-Larsen et al. 2005, Lillie et al. 2007). Using microarray expression

technology in healthy market weight pigs, we previously reported widely variable constitutive hepatic

gene expression in a number of porcine innate immune genes (chapter 2), including hepcidin

antimicrobial peptide (HAMP; encoded by the HAMP gene), retinoic acid-inducible gene 1 (RIG-1;

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encoded by the DDX58 gene), peptidoglycan recognition protein-1 (PGLYRP1; encoded by the

PGLYRP1 gene) and peptidoglycan recognition protein-2 (PGLYRP2; encoded by the PGLYRP2

gene). Because of the key role these proteins play in host defense; HAMP, DDX58, PGLYRP1 and

PGLYRP2 were selected for characterization of their 5'-upstream promoter sequences to identify

genetic variations that may underlie the observed variation in expression. Variant genotype

frequencies for the identified HAMP and DDX58 SNPs and previously reported CD169 and CD163

coding SNPs were then compared in healthy and diseased pig populations to identify significant

disease associations.


Sample Acquisition, Nucleic Acid Extraction and Primer Design

Liver samples of 1003 healthy terminally crossed commercial market weight pigs were

collected from a large southern Ontario pig processing facility as previously described (Chapter 2). As

described in Chapter 2, Nucleic acids were extracted and stored and primers were designed as

described in Chapter 3.

Amplification of the 5'-Promoter Regions of HAMP, DDX58, PGLYRP1 and PGLYRP2

Using the forward and reverse primers listed in Table 4.1, gene segments of the 5'-promoter

regions of HAMP (2587 bp), DDX58 (2643 bp), PGLYRP1 (1520 bp) and PGLYRP2 (1498 bp) were

amplified. All amplifications were performed according to the manufacturer’s recommendations (50

μL reactions; final primer concentration of 0.5 µM) using the QIAGEN TopTaq DNA Polymerase

Kit®. QIAGEN TopTaq Q-solution was added to the PCR reaction for HAMP. Cycling parameters

for all reactions were as follows: initial denaturation for 3 min at 94 ºC, followed by 35 cycles of

denaturation at 94 ºC for 30 s, annealing at 62 ºC (DDX58), 56 ºC (HAMP), 55 ºC (PGLYRP1) or 58

ºC (PGLYRP2) for 30 s and extension at either 72 ºC for 2 min and 55 s (DDX58); 2 min and 30 s

(HAMP) or 1 min and 30 s (PGLYRP1 and PGLYRP2), with a final extension at 72 ºC for 10 min. In

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this study all PCR products were visualized with agarose gel electrophoresis (1 or 2 %; 0.5 X tris-

borate-EDTA (TBE) buffer; SYBR SAFE nucleic acid stain). The PCR products of DDX58,

PGLYRP1 and PGLYRP2 were extracted from the agarose gel and purified using a QIAquick® gel

extraction kit according to manufacturer’s recommendations prior to submission for sequence

analysis.

Sequencing of PCR products and Identification of Novel SNPs.

Pigs with the highest (n = 8) and lowest (n = 8) levels of mRNA expression, as determined by

microarray analysis, were selected for pooled sequencing as described in Chapter 3. Sequencing

primers used are listed in Table 4.1. Assembled sequences were aligned using Clustal Omega -

Multiple Sequence Alignment (http://www.ebi.ac.uk/Tools/msa/clustalo/) and screened for genetic

variation as previously described (Chapter 3). Nomenclature of the identified polymorphisms was

based on their nucleotide location relative to the first ATG start codon within the coding sequence as

described by the human genome variation society (den Dunnen and Antonarakis 2000). The variant

allele was designated as the allele that varied from the reported nucleotide sequence used as reference

sequence and was not always the less common allele. In all tables, the variant allele is listed last.

Semi-Quantitative Real-Time RT-PCR

Variations in the constitutive expression of HAMP and DDX58 were also assessed using

semi-quantitative real-time RT-PCR. Reverse transcription of cDNA was performed according to the

manufacturer’s recommendations using the QuantiTect® Reverse Transcription Kit (QIAGEN,

Mississauga, Ontario) and semi-quantitative real-time RT-PCR was performed as described in

Chapter 3. RT-PCR primers and reaction efficiencies for each standard curve are listed in Table 4.2. A

reproducible standard curve could not be generated for the amplification of HAMP so semi-

quantitative real-time RT-PCR was not performed on this gene. Amplification of the desired targets

was confirmed by DNA sequencing (Lab Services Division, University of Guelph, Guelph, Ontario).

RT-PCR conditions for all reactions were as follows: pre-incubation at 95 ºC for 5 min, followed by

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45 cycles of denaturation at 95 ºC for 10 s, annealing at appropriate gene melting temperature for 10 s

(Table 4.2), and elongation at 72 ºC for 15 s, followed by melting curve analysis (65 to 95 ºC) to

confirm the presence of a single product per PCR reaction.

As described previously (Chapter 3), the RefFinder program (http://www.

leonxie.com/referencegene.php) was used to evaluate GAPDH, 28s rRNA and 2M expression to

identify the most stable reference genes in this data set. This program uses the BestKeeper (Pfaffl et

al. 2004), Normfinder (Andersen et al. 2004), Genorm (Vandesompele et al. 2002) and comparative

delta-Ct (Silver et al. 2006) methods and identified GAPDH as the most stable reference gene for

evaluation of target gene expression in this study.

The Mann-Whitney test or Kruskal-Wallis one way analysis of variance along with Dunn’s

multiple comparisons post test was used to identify differences in microarray expression between the

different genotypes of each identified genetic variant (Table 4.8). For genetic variants where only two

genotypes were available for comparison, the Mann-Whitney test was used. For genetic variants for

which three genotype groups were available, the Kruskal-Wallis one way analysis of variance and

Dunn’s multiple comparisons post test were used.

MALDI-TOF Mass Spectrometry of Diseased and Healthy Pig Populations

Comparative SNP genotyping of identified HAMP and DDX58 promoter SNPs as well as

previously reported CD163 and CD169 SNPs was performed on three distinct populations as

previously described (Chapter 3) and consisted of diseased autopsy pigs (n = 386); healthy market

weight pigs (n = 500); healthy purebred boars (n = 475)). Briefly, Sequenom MassARRAY® matrix-

assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (Sequenom, San

Diego, CA, USA) and single base extension (Gabriel et al. 2009) was performed at the UHN Clinical

Genomics Centre (Mount Sinai Hospital, Toronto, Ontario). MALDI-TOF SNP genotyping for some

polymorphisms could not be performed and genotyping comparisons could not be made for the

following variants: CD169 g.4175C>T; HAMP g.-1620G>A; HAMP g.-1123G>A; HAMP g.-

1012T>C; DDX58 g.-542C>T; DDX58 g.777-778delCA and DDX58 g.-783G>A.

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As described in Chapter 3, diseased pigs were grouped into broad disease syndrome groups

(infectious, enteric, pneumonia, polyserositis and septicemia) and by etiologic agent (Actinobacillus

pleuropneumoniae (APP) (n = 22); K88+ Escherichia coli (n = 31); Haemophilus parasuis (n = 20);

Streptococcus suis (n = 84); Salmonella enterica subsp. enterica ser. Typhimurium (Salmonella

Typhimurium) (n = 26); Mycoplasma spp. (n = 39); porcine circovirus type 2 (PCV2) (n = 84) and

porcine reproductive and respiratory syndrome virus (PRRSV) (n = 69)) and were assessed using a

one-tailed Fisher's exact probability test and 2 x 2 contingency tables and the false discovery rate was

controlled at 3 % as previously described (Chapter 3). This translated to a FDR of 1.08 false

discoveries within the 36 significant associations identified (Storey 2002, Storey 2003, Strimmer

2008).

Variant genotype frequencies within the healthy reference pig population were also compared

to that of pure bred pigs and four theoretical crossbred populations (50 % Duroc, 25 % Large White,

25 % Landrace); (50 % Landrace, 25 % Large White, 25 % Duroc); (50 % Large White; 25 %

Landrace, 25 % Duroc) and (33 % Large White, 33 % Landrace, 33 % Duroc) as described in Chapter

3. Briefly, for pure breed comparisons a five-way chi-square test (five columns two rows) was used to

identify significant differences in variant allele frequencies. If significant differences were identified a

pairwise Yates Chi-square test, using 2 x 2 contingency tables, was used to identify which specific

breeds had significantly different variant positive genotype frequencies when compared to the other

breeds tested in this study. When the expected value for one or more of the cells was < 5 a one-tailed

Fisher's exact probability test was used instead.

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Table 4.1. Primers used for promoter region amplification and sequencing of DDX58, HAMP, PGLYRP1 and PGLYRP.

Gene target Ensembl ID Primer name Nucleotide sequence (5' > 3') Amplicon length (bp)

HAMP amplification [ENSSSCT00000003189] pHAMP-2446FWD TATCCCACTGCCTCCTTG 2587

[ENSSSCT00000034173] pHAMP123REV GGTGCTGTCTGTCCGTCCA

HAMP sequencing [ENSSSCT00000003189] pHAMP123REV GGTGCTGTCTGTCCGTCCA N/A

[ENSSSCT00000034173] pHAMP-1375FWD AGAGTGAGTTGGAGGAGGAA N/A

pHAMP-1375REV TTCCTCCTCCAACTCACTCT N/A

pHAMP-1903REV GTAACACAGGAGACCCCAGCC N/A

pHAMP-2446FWD TATCCCACTGCCTCCTTG N/A

DDX58 amplification [ENSSSCT00000026775] RIG -2369FWD CAGCAGAAGGAGCAGATGGTG 2643

RIG256REV CAGGATGAAGGTGGGGTCG

DDX58 sequencing [ENSSSCT00000026775] RIG10REV AGCCCTCACTTTCCCAGCG N/A

RIG-858REV GCTAAGTAAGGGTCAAGGCT N/A

RIG-1026FWD AGATAAGTAGAACAGAATAGGC N/A

RIG-1144REV TATTGGATGAACCTGGGG N/A

RIG-1927FWD ATGTTTCCCTGCTGAGATTAGT N/A

RIG -2369 FWD CAGCAGAAGGAGCAGATGGTG N/A

PGLYRP1 amplification [ENSSSCT00000003438] PGLYRP1-1407FWD CAACAACTCAACAATCCCA 1520

PGLYRP1_94REV CACTCTCTGCGGGACACAA

PGLYRP1 sequencing [ENSSSCT00000003438] PGLYRP1-1407FWD CAACAACTCAACAATCCCA N/A

PGLYRP1_94REV CACTCTCTGCGGGACACAA N/A

PGLYRP2 amplification [ENSSSCT00000022764] PGLYRP2-1401FWD CCTGACCCCAAATCCTTAGA 1498

[ENSSSCT00000023031] PGLYRP2_77REV GCTCACCTGTTCCTGGCTCC

PGLYRP2 sequencing [ENSSSCT00000022764] PGLYRP2-1401FWD CCTGACCCCAAATCCTTAGA N/A

[ENSSSCT00000023031] PGLYRP2_77REV GCTCACCTGTTCCTGGCTCC N/A

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Table 4.2. Primers used for semi-quantitative real-time RT-PCR assays of DDX58 and HAMP.

Gene Ensembl ID Forward Primer (5' > 3') Reverse Primer (5' > 3')

Melting

temperature

(ºC)

Amplicon

length

(bp)

PCR

efficiency

DDX58 [ENSSSCT00000026775] GAACCTGTGCCTGATAAGAAAAC GTGCAGTTTACTCACAAAGCG 60 150 2.17

HAMP [ENSSSCT00000003189]

[ENSSSCT00000034173]

AGAGCGAGTCCTAGAGCTAAC GTGGCTCCTGCTGTGTCCT 56 186 N/A

B2M [ENSSSCT00000005170] TCTACCTTCTGGTCCACACTGAG TCATCCAACCCAGATGCA 60 161 1.90

GAPDH [ENSSSCT00000000756] GAAGGCTGGGGCTCACTT GTCTTCTGGGTGGCAGTGAT 60 227 2.08

28S [ENSSSCT00000006752] CGGGTAAACGGCGGGAGTAA TAGGTAGGGACAGTGGGAAT 60 294 1.83

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RESULTS

Novel SNPs and Polymorphisms in the 5'-Promoter Regions of HAMP and DDX58

Fourteen novel polymorphisms were identified in the 2441 bp of the 5'-upstream promoter

region of the HAMP gene. These genetic variations included four transversion SNPs, nine transition

SNPs and a single deletion. Appendix IV - Figure IV.3 and Table 4.3 summarizes all identified

variations. Some of the SNPs were found to be more frequent in pigs with low levels of HAMP

expression (HAMP g.-902C>G and HAMP g.-1620G>A); while others were more common in pigs

with high levels of expression (HAMP g.-947T>C; HAMP g.-1405C>G and HAMP g.-1421G>C)

(Figure 4.1). A summary of the relative frequency of these SNPs in pigs with low and high levels of

HAMP expression and of the percentage of pigs with at least one copy of the variant allele at each

SNP location is shown in Table 4.4. Within this subset of high and low expressing pigs (n = 18) four

different SNP haplotypes were also identified (Table 4.9): one in which HAMP g.-165G>A; HAMP

g.-1019G>A; HAMP g.-1123G>A; HAMP g.-2142T>C and HAMP g.-1582-

1600delCCCTGCCTCAACCAGCAGC (HAMP haplotype 1) always occurred together; haplotypes

in which either HAMP g.-902C>G and HAMP g.-1620G>A (HAMP haplotype 3) or HAMP g.-

887G>A; HAMP g.-1012T>C and HAMP g.-1540G>C (HAMP haplotype 2) were co-expressed and a

haplotype in which HAMP g.-947T>C; HAMP g.-1405C>G and HAMP g.-1421G>C (HAMP

haplotype 4) that was present only in pigs with high levels of HAMP expression. In this subset, the

polymorphisms in each haplotype were considered to be 100 % linked.

Nineteen novel polymorphisms were identified in the 2364 bp of the 5'-upstream promoter

region of the DDX58 gene. These genetic polymorphisms included four transversion SNPs, ten

transition SNPs, three deletions and two insertions. Appendix IV - Figure IV.4 and Table 4.5

summarize all identified variations. Four of these SNPs, DDX58 g.-293T>G; DDX58 g.-542C>T;

DDX58 g.-1325T>C and DDX58 g.-2089A>G as well as a single deletion g.-1063-1065delATA, were

more frequent in pigs with low levels of DDX58 expression (Figure 4.1). A summary of the

percentage of pigs with at least one copy of the variant allele at each SNP locus, as well as the total

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variant allele frequency can be found in Table 4.6. Although some of these variants often occurred

together only two SNP haplotypes could be identified in this subpopulation (n = 15) (Table 4.9).

DDX58 haplotype 2 (DDX58 g.-1325T>C, DDX58 g.-2089A>G and DDX58 g.-1063-1065delATA)

was more frequent in pigs with low levels of expression.

Sequencing of pooled samples of the eight highest and lowest expressing pigs (n = 16) did not

identify any SNPs, insertions or deletions within the 1520 and 1498 bp of the 5'-upstream promoter

region and first coding exons of PGLYRP1 and PGLYRP2 respectively (Appendix IV - Figure IV.5

and Figure IV.6).

DDX58 and HAMP mRNA Expression Levels

The variability in DDX58 mRNA expression was less extensive when measured by RT-PCR

compared to microarray analysis. The gene expression ratio, calculated by comparing the mean

expression of the top 50 % of pigs to the mean gene expression of the bottom 6 % of pigs was a 6.5

when measured by RT-PCR and 13 when measured by microarray technology. The maximum

variation between pigs with the highest and lowest RT-PCR expression was 70-fold compared to 130-

fold when assessed by the microarray method. Although measurements of gene expression using RT-

PCR and microarray techniques are usually well correlated, RT-PCR is considered to be the more

sensitive method of the two. RT-PCR is therefore often able to identify smaller changes in gene

expression and often results in larger observed variation in gene expression. This was not the case for

DDX58 expression and correlation between microarray and RT-PCR analysis for individual samples

was poor (R2 = 0.0979) (Figure 4.2). The reason for the poor correlation between microarray and RT-

PCR assays is not known but may be due to differences in the location and design of primers and

probes. Both DDX58 microarray probes were located 401 bp apart at the beginning of the 3'UTR of

exon 20 while RT-PCR primers were located upstream in exons 17 and 18. Discrepancies between

assays may also occur if some primers and probes do not recognize all splice variants and haplotypes

of these genes. In addition, results may also be confounded by interactions between different

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polymorphisms in other regions of the genes and by the presence of complex haplotypes that occur in

some, but not all, pigs. Additional studies are needed to resolve the discrepancies between these

different technologies. Despite the poor correlation between these two methods a high degree of

correlation was observed between the two different microarray probes. The correlation coefficient

(R2) for assays performed using these two probes was 0.8402 (Figure 4.3) and variations in mRNA

expression were evaluated based on microarray expression alone.

HAMP mRNA expression was quantified using two different (non-identical) microarray

probes located 30-bp apart at the 3'-end of the 3rd exon of the two splice variants of this gene.

Microarray quantification using these probes was considered to encompass both known porcine

transcript variants. The results obtained using these two probes were strongly correlated (R = 0.9760)

(Figure 4.4). HAMP RT-PCR primer design was focussed on the 5'-UTR and first two exons of the

HAMP gene, a common shared region of both transcripts to accommodate for this variation. Despite

multiple attempts and primer sets, generation of a consistent standard curve could not be attained. As

a result, variations in mRNA expression were evaluated based on microarray expression alone.

Animals that were heterozygous (n = 15) and homozygous (n = 2) for the HAMP g.-947T>C,

HAMP g.-1405C>G and HAMP g.-1421G>C SNPs (HAMP haplotype 4) showed an increase in

hepatic expression when compared to the wild type allele (n = 71) with the increase in heterozygous

individuals being statistically significant (p = 0.0152) (Figure 4.1B). The lack of statistical

significance in homozygous individuals is likely due to low sample size. Animals that were

heterozygous (n = 9) for the HAMP g.-902C>G SNP showed a decrease in hepatic expression when

compared to the wild type allele (n = 79) and trended towards statistical significance (p = 0.0803)

(Figure 4.1A). No homozygous individuals were available for comparison. Animals that were

heterozygous (n = 32) for the DDX58 g.-1325T>C, DDX58 g.-1063delATA and DDX58 g.-2089A>G

polymorphisms (DDX58 haplotype 2) showed a significant decrease in hepatic expression when

compared to the wild type allele (n = 56) (p = 0.0104) (Figure 4.1D). No homozygous individuals

were identified in this subset of pigs. Animals that were heterozygous (n = 39) and homozygous (n =

4) for the DDX58 g.-293T>G SNP showed a decrease in hepatic expression when compared to the

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wild type allele (n = 45) however, the differences were not statistically significant (p = 0.8831 and p =

0.8826) (Figure 4.1C).

MALDI-TOF Mass Spectrometry of Diseased and Healthy Pig Populations

The SNPs identified were genotyped using MALDI-TOF mass spectrometry in diseased pigs,

healthy cross bred and pure bred pigs as described previously. The same DDX58 haplotypes

(haplotype 1 and 2) as previously identified also occurred within this larger population of genotyped

pigs and were 100 % linked across all genotyped pig populations (Table 4.9). Similar results were

also obtained for the HAMP gene however some SNPs, previously allocated to specific haplotypes

(HAMP g.-1123G>A, HAMP g.-1012T>C SNPs and HAMP g.-1620G>A), could not be assessed in

the larger group of genotyped populations. Due to the absence of the HAMP g.-1123G>A and HAMP

g.-1012T>C SNPs from our genotyping data, these haplotypes were renamed as haplotype 1A and 2A

respectively and HAMP g.-902C>G (HAMP haplotype 3) was assessed individually. The HAMP g.-

947T>C; HAMP g.-1405C>G and HAMP g.-1421G>C SNPs (HAMP haplotype 4) often occurred

together and exhibited near identical disease associations however were not 100 % linked in all

genotyped populations and formed three closely related haplotypes (HAMP haplotype 4A, 4B, and

4C). Similarly the DDX58 g.-194-195insGAGGG (DDX58 haplotype 1A) and DDX58 g.-817G>A

(DDX58 haplotype 1B) variants also often occurred together with the genetic variants composing

DDX58 haplotype 1, again with near identical disease associations, however were also not 100 %

linked. Two more SNPs, DDX58 g.-86A>C and DDX58 g.-1309A>C (DDX58 haplotype 3) were also

not 100 % linked however again had near identical disease associations. A summary of all identified

haplotypes and their associated linkage can be found in Table 4.9.

Table 4.10 to 4.14 summarize all the genotyping comparisons and calculated p- and q-values

for HAMP, DDX58, CD163 and CD169. When compared to the healthy reference pig population the

G allele of HAMP g.-902C>G was more frequent in the infectious disease, pneumonia, polyserositis

and septicemia disease groups with the first two being statistically significant after correcting for the

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FDR. When compared to specific pathogen groups; the G allele was approximately 2.8, 1.8 and 2.0

times more frequent in the Mycoplasma spp., PCV2 and PRRSV pathogen groups respectively

however the PRRSV association was not statistically significant. Variant alleles of the HAMP

haplotype 2A was significantly less frequent in the infectious, pneumonia and septicemia disease

groups and PCV2 pathogen group. Decreased frequencies of this haplotype were also observed within

in the enteric, polyserositis and Mycoplasma spp. groups and trended towards statistical significance.

HAMP haplotype 1A and the three SNPs previously associated with increased hepatic expression

(HAMP g.-947T>C, HAMP g.-1405C>G and HAMP g.-1421G>C) were not associated with any

statistically significant changes in variant allele frequency in the different disease groups. HAMP

haplotype 1A was however approximately eight times less frequent in the K88+ E. coli pathogen

group while the other three SNPs were significantly less frequent in the PCV2 pathogen group.

When compared to the healthy reference pig population the G allele of DDX58 g.-293T>G

was more frequent in the infectious, septicemia, pneumonia and enteric disease groups and 1.5 times

more frequent in both the Salmonella Typhimurium and Haemophilus parasuis pathogen groups

however the pneumonia, enteric and H. parasuis groups were not statistically significant. The A allele

of DDX58 g.-309G>A was significantly less frequent in the infectious, enteric and pneumonia disease

groups and approximately 2 and 1.3 times less frequent in the K88+ E. coli and PCV2 pathogen

groups respectively. The A allele was also decreased in the APP, H. parasuis and S. Typhimurium

pathogen groups however only the latter two trended towards statistical significance. DDX58 g.-

817G>A, DDX58 g.-194-195insGAGGG and DDX58 haplotype 1 had no statistically significant

changes in variant allele frequency in the different disease groups but statistically significant changes

were observed for some pathogen groups with the variant allele being approximately twice as frequent

in both the K88+ E. coli and S. Typhimurium pathogen groups. Although no statistically significant

variations in variant allele frequency of the DDX58 g.-1748-1751delGAGA, DDX58 g.-86A>C,

DDX58 g.-1309A>C and DDX58 haplotype 2 variants were identified in the tested disease syndrome

groups, statistically significant changes were observed for some pathogen groups. The C allele of both

DDX58 g.-86A>C and DDX58 g.-1309A>C was 3.5 and 3.4 times less frequent in the K88+ E. coli

pathogen group respectively and the GAGA deletion of the DDX58 g.-1748-1751delGAGA variant

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was 1.4 times less frequent in the H. parasuis pathogen group. Variant alleles of DDX58 haplotype 2

were 1.9 times more frequent in the H. parasuis pathogen group and 1.3 times more frequent in the

septicemia disease group and with the latter only tending towards statistical significance.

A recent study (Ren et al. 2012) reported specific CD163 and CD169 polymorphism

genotypes that were associated with resistance to PRRSV infection in commercial Chinese crossbred

pigs (Duroc X Landrace X Large White) and these SNPs were also tested in this study to determine if

the sample SNPs were present in North American pigs and what impact they had on infectious disease

resistance. These genotypes included the AA of CD169 g.1654C>A, CT of CD169 g.4175C>T and

AA of CD163 g.2552A>G. The CD169 (Siglec-1) sialoadhesin, present on macrophage cell

membranes, interacts with sialic acids present on the surface of PRRSV thereby mediating its

attachment in a clathrin-dependent manner and ultimately resulting in internalization of the virus

along with its receptor (De Baere et al. 2012, Delputte and Nauwynck 2004, Vanderheijden et al.

2003). CD163 is a macrophage-specific scavenger receptor belonging to the cysteine-rich receptor

superfamily and functions as a cellular receptor for PRRSV as well as assisting in uncoating of the

virus and subsequent cellular replication (Welch and Calvert 2010). When compared to the healthy

reference pig population, the G allele of CD163 g.2552A>G was significantly more frequent in the

PRRSV pathogen group (1.4 times) and all disease groups except polyserositis. The G allele was also

more frequent in most of the remaining pathogen groups (approximately 1.8 times in APP, 1.3 times

in Streptococcus suis and 1.2 times in PCV2, K88+ E. coli and Mycoplasma spp.) however none were

statistically significant with the APP, S. suis and PCV2 associations tending towards significance. The

A allele of the CD169 g.1654C>A SNP did not vary significantly between different disease groups

and most pathogens however was approximately 1.2 times more frequent in the K88+ E. coli

pathogen group in which case the association trended towards statistical significance. Genotyping

failed for the CD169 g.4175C>T SNP and could not be further assessed.

With the exception of DDX58 g.-293 G>T in the Hampshire and Landrace breeds, all

genotyped HAMP, DDX58, CD169 and CD163 polymorphisms were represented in all examined

North American purebred boars. Variant genotype frequency varied significantly between the

138

different purebred pig breeds included in this study (Table 4.16 and Table 4.17). Three

polymorphisms displayed less variable frequencies between breeds: variant positive genotype

frequencies of the G allele of HAMP g.-902C>G ranged from 6.0 % (Large White) to 19.0 %

(Landrace) while the GAGA deletion of DDX58 g.-1748-1751delGAGA ranged from 79.0 % (Large

White) to 91.8 % (Pietrain). The third, DDX58 g.-219T>G SNP, was found to be extremely rare

across all genotyped pig populations and the G allele frequency ranged from 0.0 (Landrace) to only

2.0 % (Large White) with no homozygous individuals identified. Variant genotype frequencies were

also compared to that of different weighted purebred crosses in an attempt to see how closely our

commercial population of crossbred pigs compared to that of commonly implemented cross breeding

strategies. Variant genotype frequencies of the different weighted crossbred pig populations were

found to be more similar to that observed with our healthy market weight pig population (Table 4.18).

Individuals that were homozygous for the variant allele were rare in almost all identified promoter

polymorhisms and included CD163 g.2552A>G (69 individuals or 5.1 %; n = 1358); HAMP

haplotype 1A (23 individuals or 1.7 %; n = 1356); HAMP g.-947T>C (54 individuals or 3.9 %; n =

1358); HAMP g.-1405C>G (51 individuals or 3.8 %; n = 1357); HAMP g.-1421G>C (51 individuals

or 3.8 %; n = 1358); HAMP haplotype 2A (159 individuals or 11.8 %; n = 1353); HAMP g.-902C>G

(8 individuals or 0.6 %; n = 1358); DDX58 g.-219T>G (0 individuals or 0.0%; n = 1358); DDX58 g.-

309G>A (119 individuals or 8.8 %; n = 1356); DDX58 g.-293T>G (111 individuals or 8.2 %; n =

1358); DDX58 g.-817G>A (39 individuals or 2.9 %; n = 1355); DDX58 g.-194-195insGAGGG (10

individuals or 0.7 %; n = 1358); DDX58 haplotype 1 (10 individuals or 0.7 %; n = 1354); DDX58 g.-

86A>C (15 individuals or 1.1 %; n = 1357); DDX58 g.-1309A>C (15 individuals or 1.1 %; n = 1356)

and DDX58 haplotype 2 (47 individuals or 3.5 %; n = 1352).

139

Table 4.3. Identified HAMP sequence variations.


HAMP g.-165G>A Transition SNP Promoter



HAMP g.-902C>G Transversion SNP Promoter

HAMP g.-947T>C Transition SNP Promoter




HAMP g.-1405C>G Transversion SNP Promoter

HAMP g.-1421G>C Transversion SNP Promoter

HAMP g.-1540G>C Transversion SNP Promoter

HAMP g.-1582-1600delCCCTGCCTCAACCAGCAGC Deletion (19 bp) Promoter



Nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000).

140

Table 4.4. Relative allele frequencies of HAMP promoter variants between high and low expressing groups.

Promoter variants that were more frequent in low or high expressing groups are underlined.

Genotype Low (n = 9) High (n = 9)

% variant positive variant allele

frequency % variant positive

variant allele

frequency

HAMP g.-165G>A 22 0.1 11 0.1

HAMP g.-271G>A 78 0.5 100 0.6

HAMP g.-887G>A 33 0.2 44 0.2

HAMP g.-902C>G 33 0.2 11 0.1

HAMP g.-947T>C 0 0.0 44 0.2

HAMP g.-1012T>C 33 0.2 44 0.2

HAMP g.-1019G>A 22 0.1 11 0.1

HAMP g.-1123G>A 22 0.1 11 0.1

HAMP g.-1405C>G 0 0.0 44 0.2

HAMP g.-1421G>C 0 0.0 44 0.2

HAMP g.-1540G>C 33 0.2 44 0.2

HAMP g.-1582-1600delCCCTGCCTCAACCAGCAGC 22 0.1 11 0.1

HAMP g.-1620G>A 33 0.2 11 0.1

HAMP g.-2142T>C 22 0.1 11 0.1

141

Table 4.5. Identified DDX58 sequence variations.


DDX58 g.-86A>C Transversion SNP Promoter

DDX58 g.-194-195insGAGGG Insertion (5 bp) Promoter

DDX58 g.-219T>G Transversion SNP Promoter

DDX58 g.-293T>G Transversion SNP Promoter

DDX58 g.-309G>A Transition SNP Promoter

DDX58 g.-542C>T Transition SNP Promoter


DDX58 g.777-778delCA Deletion (2 bp) Promoter



DDX58 g.-997C>T Transition SNP Promoter

DDX58 g.-1063-1065delATA Deletion (3 bp) Promoter

DDX58 g.-1309A>C Transversion SNP Promoter

DDX58 g.-1325T>C Transition SNP Promoter

DDX58 g.-1748-1751delGAGA Deletion (4 bp) Promoter

DDX58 g.-1821-1822insTAAAA Insertion (5 bp) Promoter


DDX58 g.-2089A>G Transition SNP Promoter

DDX58 g.-2229A>G Transition SNP Promoter

Nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000).

142

Table 4.6. Relative allele frequencies of DDX58 promoter variants between high and low expressing groups.

Promoter variants that were more frequent in low expressing groups are underlined.

Genotype Low (n = 9) High (n = 6)

% variant positive variant allele

frequency % variant positive

variant allele

frequency

DDX58 g.-86A>C 22 0.1 33 0.2

DDX58 g.-194-195insGAGGG 100 0.9 100 0.9

DDX58 g.-219T>G 100 1.0 83 0.8

DDX58 g.-293T>G 56 0.3 33 0.2

DDX58 g.-309G>A 22 0.1 33 0.3

DDX58 g.-542C>T 44 0.2 17 0.1

DDX58 g.-631G>A 100 0.9 100 0.9

DDX58 g.-777-778delCA 22 0.1 17 0.1

DDX58 g.-783G>A 100 0.9 83 0.8

DDX58 g.-817G>A 100 0.9 83 0.8

DDX58 g.-997C>T 100 0.9 100 0.9

DDX58 g.-1063-1065delATA 56 0.3 17 0.1

DDX58 g.-1309A>C 22 0.1 33 0.2

DDX58 g.-1325T>C 56 0.3 17 0.1

DDX58 g.-1748-1751delGAGA 100 0.5 75 0.4

DDX58 g.-1821-1822insTAAAA 100 0.9 100 0.9

DDX58 g.-1994G>A 100 0.9 100 0.9

DDX58 g.-2089A>G 56 0.3 17 0.1

DDX58 g.-2229A>G 100 0.9 100 0.9

143

Table 4.7. Mean hepatic gene expression of HAMP and DDX58 in variant genotypes.

Relationship between mean relative hepatic expression of HAMP and DDX58 and identified promoter polymorphisms. Mean gene expression was calculated

using microarray expression relative to that of the housekeeping gene GAPDH. W = wild type allele/s and V = variant allele/s.

Genotype Homozygous Wild Type (WW) Heterozygous Variant (WV) Homozygous Variant (VV)

Mean

expression

Standard

deviation n =

Mean

expression

Standard

deviation n =

Mean

expression

Standard

deviation n =

HAMP haplotype 1A 1.36 1.35 71 1.10 0.91 17 N/A N/A 0

HAMP haplotype 2A 1.24 1.05 42 1.50 1.54 40 0.56 0.28 6

HAMP haplotype 4 1.22 1.35 71 1.72 0.85 15 1.44 0.91 2

HAMP g.-271G>A 0.93 0.54 17 1.37 1.46 55 1.52 1.11 16

HAMP g.-902C>G 1.38 1.32 79 0.76 0.62 9 N/A N/A 0

DDX58 g.-1748-1751delGAGA 1.01 0.73 11 1.14 0.73 50 1.15 0.79 27

DDX58 g.-219T>G 1.29 1.27 87 N/A N/A 0 3.16 N/A 1

DDX58 g.-309G>A 1.15 0.69 53 0.97 0.58 29 1.85 1.84 4

DDX58 g.-293T>G 1.21 0.78 45 1.07 0.73 39 0.83 0.21 4

DDX58 g.-817G>A 1.10 0.75 71 1.20 0.57 13 1.41 1.12 4

DDX58 haplotype 1A 1.10 0.75 71 1.25 0.70 17 N/A N/A 0

DDX58 haplotype 2 1.26 0.77 56 0.89 0.63 32 N/A N/A 0

DDX58 haplotype 3 1.10 0.74 67 1.26 0.75 20 0.60 N/A 1

144

Table 4.8. Effect of variant genotype on HAMP and DDX58 expression.

Significant differences in microarray expression between the different genotypes of each identified

genetic variant identified in this population were assessed. For two-way comparisons the Mann-

Whitney test was used while three way comparisons were assessed using the Kruskal-Wallis one-way

analysis of variance along with a Dunn’s multiple comparisons post test. For haplotypes W = wild

type alleles; V = variant alleles. * indicates a significant difference at p < 0.05.

Variant Statistical test p-value Dunn's post test p-value

HAMP haplotype 1A Mann-Whitney 0.4789 N/A N/A

HAMP haplotype 2A Kruskal-Wallis 0.0538 GG vs. GA 0.7339

GG vs. AA 0.2324

GA vs. AA 0.0568

HAMP haplotype 4 Kruskal-Wallis 0.0165* WW vs. WV 0.0152*

WW vs. VV > 0.9999

WV vs. VV > 0.9999

HAMP g.-271G>A Kruskal-Wallis 0.3516 GG vs. GA > 0.9999

GG vs. AA 0.4559

GA vs. AA 0.8738

HAMP g.-902C>G Mann-Whitney 0.0803 N/A N/A

DDX58 g.-1748-1751delGAGA Mann-Whitney 0.6547 GAGA vs. GAGA/DEL > 0.9999

GAGA vs. DEL > 0.9999

GAGA/DEL vs. DEL > 0.9999

DDX58 g.-309G>A Kruskal-Wallis 0.4273 GG vs. GA 0.6552

GG vs. AA > 0.9999

GA vs. AA > 0.9999

DDX58 g.-293T>G Kruskal-Wallis 0.3982 TT vs. GT 0.8831

TT vs. GG 0.8826

GT vs. GG > 0.9999

DDX58 g.-817G>A Kruskal-Wallis 0.6774 GG vs. AG > 0.9999

GG vs. AA > 0.9999

GG vs. AG > 0.9999

DDX58 haplotype 1A Mann-Whitney 0.3804 N/A N/A

DDX58 haplotype 2 Mann-Whitney 0.0104* N/A N/A

DDX58 haplotype 3 Mann-Whitney 0.2019 N/A N/A

145

Figure 4.1. Hepatic expression of HAMP and DDX58 with respect to polymorphism genotypes.

Relationship between mean relative hepatic microarray expression of HAMP and DDX58 and selected

polymorphisms found to be more frequent in pigs with either decreased or increased expression of

HAMP and DDX58.

A: Animals that were heterozygous (n = 9) for the HAMP g.-902C>G SNP showed a decrease in

hepatic expression when compared to the wild type allele (n = 79) and trended towards significance (p

= 0.0803). No homozygous individuals were identified in this subset of pigs.

B: Animals that were heterozygous (n = 15) for the HAMP g.-947T>C, HAMP g.-1405C>G and

HAMP g.-1421G>C SNPs (HAMP haplotype 4) showed a significant increase in hepatic expression

when compared to the wild type allele (n = 71) (p = 0.0152). Homozygous animals (n = 2) also

showed had an increase in hepatic expression, however this change was not statistically significant (p

> 0.9999).* indicates a significant difference at p < 0.05.

C: Animals that were heterozygous (n = 39) and homozygous (n = 4) for the DDX58 g.-293T>G SNP

showed a decrease in hepatic expression when compared to the wild type allele (n = 45) however was

not statistically significant (p = 0.8831 and p = 0.8826 respectively).

D: Animals that were heterozygous (n = 32) for the DDX58 g.-1325T>C, DDX58 g.-1063delATA and

DDX58 g.-2089A>G polymorphisms (DDX58 haplotype 2) showed a significant decrease in hepatic

expression when compared to the wild type allele (n = 56) (p = 0.0104). No homozygous individuals

were identified in this subset of pigs. * indicates a significant difference at p < 0.05.

146

Table 4.9. Co-expressing haplotypes identified for HAMP and DDX58 promoter

polymorphisms.

Haplotypes Polymorphisms Linkage (n = )

HAMP haplotype 1 HAMP g.-165G>A

HAMP g.-1019G>A

HAMP g.-1123G>A

HAMP g.-2142T>C

HAMP g.-1582-1600delCCCTGCCTCAACCAGCAGC

100 %

(18/18)

HAMP haplotype 1A HAMP g.-165G>A

HAMP g.-1019G>A

HAMP g.-2142T>C

HAMP g.-1582-1600delCCCTGCCTCAACCAGCAGC

100 %

(1365/1365)

HAMP haplotype 2 HAMP g.-887G>A

HAMP g.-1012T>C

HAMP g.-1540G>C

100 %

(18/18)

HAMP haplotype 2A HAMP g.-887G>A

HAMP g.-1540G>C

100 %

(1357/1357)

HAMP haplotype 3 HAMP g.-902C>G

HAMP g.-1620G>A

100 %

(18/18)

HAMP haplotype 4 HAMP g.-947T>C

HAMP g.-1405C>G

HAMP g.-1421G>C

100 %

(88/88)

HAMP haplotype 4A HAMP g.-947T>C

HAMP g.-1405C>G

99.27 %

(1355/1365)

HAMP haplotype 4B HAMP g.-1405C>G

HAMP g.-1421G>C

99.93%

(1364/1365)

HAMP haplotype 4C HAMP g.-947T>C

HAMP g.-1421G>C

99.20 %

(1358/1369)

DDX58 haplotype 1 DDX58 g.-631G>A

DDX58 g.-997C>T

DDX58 g.-1821-1821insTAAAA

DDX58 g.-1994G>A

DDX58 g.-2229A>G

100 %

(15/15 and 1367/1367)

DDX58 haplotype 1A

DDX58 haplotype 1

DDX58 g.-194-195insGAGGG

99.93 %

(1360/1361)

DDX58 haplotype 1B

DDX58 haplotype 1

DDX58 g.-817G>A

97.65 %

(1327/1359)

DDX58 haplotype 2 DDX58 g.-1325T>C

DDX58 g.-1063-1065delATA

DDX58 g.-2089A>G

100 %

(15/15 and 1354/1354)

DDX58 haplotype 3 DDX58 g.-86A>C

DDX58 g.-1309A>C

99.78 %

(1354/1357)

147

Table 4.10. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169 polymorphisms in diseased groups.

Comparison of the percentage of animals with at least one variant allele between the healthy reference population and different disease groups. Bolded text

indicates the variant allele is significantly more frequent in the diseased group (p < 0.05; FDR < 0.03). Bolded and underlined text indicates the variant allele

is significantly less frequent in the diseased group (p < 0.05; FDR < 0.03). Underlined text indicates associations with calculated p-values < 0.05 that were not

statistically significant after correcting for the FDR (i.e. q > 0.03). 1,2,3

etc. represent number of animals with a miss call for that SNP in that group (e.g. in the

healthy control group, the DDX58 g.-309G>A had 2 miscalls meaning the number of data points is = 500 −2 or 498).

Genotype

Healthy

market pigs

(n = 500)

Infectious

disease

(n = 358)

Enteric disease

(n = 182)

Pneumonia

(n = 244)

Polyserositis

(n = 56)

Septicemia

(n = 92)

CD163 g.2552A>G 39.8 50.62

49.21

52.52 45.5

1 54.9

1

CD169 g.1654C>A 76.4 77.82

77.91

78.12

70.91

72.51

HAMP haplotype 1A 24.6 20.63

19.63

20.73

21.4 27.2

HAMP g.-947T>C 23.8 21.81

25.41

20.61

17.9 25.0

HAMP g.-1405C>G 23.4 21.92

25.62

20.72

17.9 25.0

HAMP g.-1421G>C 23.4 22.11

26.01

20.61

17.9 25.0

HAMP haplotype 2A 58.4 48.64 50.6

4 46.3

4 48.2 45.11

HAMP g.-271G>A 71.2 73.32

75.11

72.72

70.91

72.51

HAMP g.-902C>G 8.2 13.82 11.1

2 14.9

2 17.9 14.1

DDX58 g.-1748-1751delGAGA 87.2 84.75

84.25

85.84

87.5 82.41

DDX58 g.-219T>G 0.8 0.32

0.62

0.42

0.0 0.0

DDX58 g.-309G>A 51.82

42.91

40.31

43.61 51.8 45.7

DDX58 g.-293T>G 44.6 50.62 48.9

2 50.0

2 44.6 58.7

DDX58 g.-817G>A 17.81

19.54

21.94

17.94

14.3 22.01

DDX58 g.-194-195insGAGGG 17.4 19.42

22.11

17.82

12.71

22.01

DDX58 haplotype 1 17.6 19.06

21.94

17.26

12.71

20.23

DDX58 g.-86A>C 22.6 18.93

20.73

20.33

16.1 20.7

DDX58 g.-1309A>C 22.61

18.33

19.63

19.82

16.1 19.6

DDX58 haplotype 2 31.11

35.97

32.04

36.37

33.32

41.12

148

Table 4.11. Calculated p- and q-values for HAMP, DDX58, CD163 and CD169 polymorphisms in diseased groups.

Bolded text indicates the variant allele is significantly more frequent in the diseased group (p < 0.05; FDR < 0.03). Bolded and underlined text indicates the

variant allele is significantly less frequent in the diseased group (p < 0.05; FDR < 0.03). Underlined text indicates associations with calculated p-values < 0.05

that were not statistically significant after correcting for the FDR (i.e. q > 0.03).

Genotype Infectious

(n = 358)

Enteric disease

(n = 182)

Pneumonia

(n = 244)

Polyserositis

(n = 56)

Septicemia

(n = 92)

p-value q-value p-value q-value p-value q-value p-value q-value p-value q-value

CD163 g.2552A>G 0.0011 0.0028 0.0181 0.0251 0.0007 0.0016 0.2514 0.066 0.0052 0.0087

CD169 g.1654C>A 0.3453 0.0469 0.3824 0.0623 0.3382 0.0609 0.2274 0.066 0.2517 0.0741

HAMP haplotype 1 0.0963 0.0281 0.1013 0.0439 0.1424 0.0451 0.3669 0.0768 0.3426 0.0799

HAMP g.-947T>C 0.2792 0.0441 0.3668 0.0615 0.187 0.0499 0.2048 0.066 0.4481 0.0841

HAMP g.-1405C>G 0.3345 0.0465 0.3137 0.0584 0.2294 0.0532 0.224 0.066 0.4153 0.083

HAMP g.-1421G>C 0.3624 0.0481 0.2757 0.0558 0.221 0.0526 0.224 0.066 0.4153 0.083

HAMP haplotype 2A 0.0028 0.0035 0.0427 0.0359 0.0012 0.0016 0.094 0.066 0.0126 0.0141

HAMP g.-271G>A 0.2739 0.0439 0.1799 0.0473 0.3661 0.0623 0.5373 0.0867 0.4526 0.0843

HAMP g.-902G>C 0.0064 0.0039 0.1539 0.0465 0.0045 0.0038 0.0229 0.066 0.0579 0.0388

DDX58 g.-1748-1751delGAGA 0.1735 0.037 0.1886 0.0475 0.3424 0.0611 0.5748 0.0883 0.145 0.0618

DDX58 g.-219G>T 0.3094 0.0455 0.6017 0.0882 0.4748 0.069 0.6532 0.0991 0.5079 0.0928

DDX58 g.-309G>A 0.0059 0.0039 0.0052 0.0143 0.0219 0.014 0.5543 0.0874 0.1657 0.0649

DDX58 g.-293T>G 0.0492 0.0198 0.1832 0.0474 0.0961 0.0377 0.5523 0.0873 0.0003 0.0009

DDX58 g.-817G>A 0.2994 0.0451 0.1403 0.046 0.5271 0.0716 0.3258 0.0735 0.2125 0.0706

DDX58 g.-194-195insGAGGG 0.2571 0.043 0.1014 0.0439 0.4886 0.0697 0.2518 0.066 0.1841 0.0674

DDX58 haplotype 1 0.3276 0.0463 0.1249 0.0453 0.4948 0.0701 0.2404 0.066 0.3221 0.0788

DDX58 g.-86A>C 0.1087 0.0296 0.3368 0.0599 0.274 0.0568 0.1718 0.066 0.3975 0.0823

DDX58 g.-1309A>C 0.0728 0.0246 0.2268 0.0516 0.2199 0.0526 0.1699 0.066 0.3073 0.0779

DDX58 haplotype 2 0.0807 0.0259 0.441 0.0679 0.0926 0.037 0.4198 0.0805 0.0415 0.0326

149

Table 4.12. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169 polymorphisms in pigs diagnosed with different bacterial

pathogens.

Comparison of the percentage of animals with at least one variant allele between the healthy reference population and different bacterial pathogen groups.



that were not statistically significant after correcting for the FDR (i.e. q > 0.03). 1,2,3

etc. represent number of animals with a miss call for that SNP in that

group (e.g. in the healthy control group, the DDX58 g.-309G>A had 2 miscalls meaning the number of data points is = 500 −2 or 498).

Genotype

Healthy

market pigs

(n = 500)

APP

(n = 22)

K88+ E. coli

(n = 31)

Haemophilus

parasuis

(n = 20)

Streptococcus

suis

(n = 84)

Salmonella

Typhimurium

(n = 26)

Mycoplasma

spp.

(n = 39)

CD163 g.2552A>G 39.8 68.2 48.4 40.0 52.4 42.3 46.2

CD169 g.1654C>A 76.4 77.3 90.3 75.0 77.4 69.2 64.1

HAMP haplotype 1A 24.6 36.4 3.2 22.22

20.2 28.01

20.5

HAMP g.-947T>C 23.8 18.2 22.6 15.0 21.4 30.8 25.6

HAMP g.-1405C>G 23.4 18.2 22.6 16.72

21.4 32.01

25.6

HAMP g.-1421G>C 23.4 18.2 22.6 15.0 21.4 30.8 25.6

HAMP haplotype 2A 58.4 45.5 54.8 50.02

50.0 44.01

39.51

HAMP g.-271G>A 71.2 72.7 83.9 80.0 75.0 76.9 69.2

HAMP g.-902C>G 8.2 13.6 9.7 5.62

14.3 16.01

23.1

DDX58 g.-1748-1751delGAGA 87.2 86.4 83.9 61.12 88.1 80.0

1 84.2

1

DDX58 g.-219T>G 0.8 0.0 0.0 5.62

0.0 0.01

0.0

DDX58 g.-309G>A 51.82

36.4 25.8 30.0

47.6 34.6 43.6

DDX58 g.-293T>G 44.6 59.1 51.6 66.72

50.0 68.01 43.6

DDX58 g.-817G>A 17.81

22.7 38.7 22.22

19.0 40.01 7.9

1

DDX58 g.-194-195insGAGGG 17.4 22.7 38.7 20.0 19.0 38.5 10.3


38.7 22.22

18.11

40.01 7.9

1

DDX58 g.-86A>C 22.6 22.7 6.5 27.82

19.0 20.01

23.1

DDX58 g.-1309A>C 22.61

22.7 6.71 26.3

1 19.0 20.0

1 20.5


36.4 29.0 58.83 34.9

1 32.0

1 36.8

1

150

Table 4.13. Calculated p- and q-values for HAMP, DDX58, CD163 and CD169 polymorphisms in pigs diagnosed with different bacterial pathogens.




Genotype APP

(n = 22)

K88+ E. coli

(n = 31)

Haemophilus

parasuis

(n = 20)

Streptococcus

suis

(n = 84)

Salmonella

Typhimurium

(n = 26)

Mycoplasma spp.

(n = 39)

p-value q-value p-value q-value p-value q-value p-value q-value p-value q-value p-value q-value

CD163 g.2552A>G 0.0080

0.0423 0.2233 0.0902 0.5792 0.0724 0.0209 0.0452 0.4754 0.1257 0.2693 0.0966

CD169 g.1654C>A 0.5804 0.1733 0.0498 0.0290 0.5314 0.0700 0.4843 0.0581 0.2668 0.0996 0.0671 0.0626

HAMP haplotype 1 0.1594 0.1556 0.0022 0.0064 0.5373 0.0701 0.2358 0.0573 0.4276 0.1210 0.3618 0.1021

HAMP g.-947T>C 0.3777 0.1694 0.5385 0.1431 0.2702 0.0620 0.3747 0.0579 0.2748 0.1004 0.4626 0.1060

HAMP g.-1405C>G 0.3942 0.1698 0.5589 0.1453 0.3684 0.0661 0.4053 0.0580 0.2232 0.0942 0.4400 0.1052

HAMP g.-1421G>C 0.3942 0.1698 0.5589 0.1453 0.2839 0.0627 0.4053 0.0580 0.2589 0.0987 0.4400 0.1052

HAMP haplotype 2A 0.1628 0.1560 0.4165 0.1276 0.3175 0.0642 0.0937 0.0551 0.1127 0.0712 0.0182 0.0350

HAMP g.-271G>A 0.5466 0.1729 0.0895 0.0464 0.2816 0.0626 0.2825 0.0576 0.3515 0.1121 0.4602 0.1059

HAMP g.-902G>C 0.2806 0.1657 0.4838 0.1367 0.5626 0.0705 0.0612 0.0533 0.1573 0.0828 0.0060 0.0230

DDX58 g.-1748-1751delGAGA 0.5534 0.1729 0.3761 0.1213 0.0062 0.0148 0.4924 0.0581 0.2210 0.0939 0.3719 0.1026

DDX58 g.-219G>T 0.8414 0.2325 0.7856 0.1928 0.1627 0.0537 0.5364 0.0609 0.8222 0.1876 0.7399 0.1497

DDX58 g.-309G>A 0.1148 0.1475 0.0039 0.0064 0.0451 0.0307 0.2768 0.0575 0.0652 0.0524 0.2055 0.0907

DDX58 g.-293T>G 0.1320 0.1511 0.2815 0.1037 0.0541 0.0321 0.2112 0.0571 0.0183 0.0201 0.5200 0.1111

DDX58 g.-817G>A 0.3629 0.1689 0.0069 0.0064 0.4110 0.0674 0.4455 0.0580 0.0099 0.0166 0.0820 0.0661

DDX58 g.-194-195insGAGGG 0.3427 0.1683 0.0057 0.0064 0.4752 0.0689 0.4073 0.0580 0.0114 0.0166 0.1789 0.0873

DDX58 haplotype 1 0.5245 0.1725 0.0062 0.0064 0.4007 0.0671 0.5106 0.0581 0.0091 0.0166 0.0874 0.0672

DDX58 g.-86A>C 0.5803 0.1733 0.0205 0.0146 0.3919 0.0668 0.2840 0.0576 0.4934 0.1273 0.5393 0.1137

DDX58 g.-1309A>C 0.5823 0.1733 0.0244 0.0162 0.4431 0.0682 0.2809 0.0576 0.4913 0.1271 0.4696 0.1062

DDX58 haplotype 2 0.3768 0.1694 0.4944 0.1380 0.0186 0.0221 0.2799 0.0576 0.5385 0.1314 0.2840 0.0977

151

Table 4.14. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169 polymorphisms in pigs diagnosed with different viral

pathogens.

Comparison of the percentage of animals with at least one variant allele between the healthy reference population and different bacterial pathogen groups



that were not statistically significant after correcting for the FDR (i.e. q > 0.03). 1,2,3

etc. represent number of animals with a miss call for that SNP in that

group (e.g. in the healthy control group, DDX58 g.-309G>A had 2 miscalls meaning the number of data points is = 500 −2 or 498).

Genotype

Healthy

market pigs

(n = 500)

PCV2

(n = 84)

PRRSV

(n = 69)

CD163 g.2552A>G 39.8 49.41

55.22

CD169 g.1654C>A 76.4 72.31

77.62


22.42

HAMP g.-947T>C 23.8 14.51 19.1

1

HAMP g.-1405C>G 23.4 14.3 19.11

HAMP g.-1421G>C 23.4 14.51 19.1

1

HAMP haplotype 2A 58.4 42.72 50.7

2

HAMP g.-271G>A 71.2 71.11

74.62

HAMP g.-902C>G 8.2 15.5 16.21

DDX58 g.-1748-1751delGAGA 87.2 85.42

80.62

DDX58 g.-219T>G 0.8 0.0 0.01

DDX58 g.-309G>A 51.82

38.61 52.9

1

DDX58 g.-293T>G 44.6 50.0 51.51

DDX58 g.-817G>A 17.81

18.32

20.92

DDX58 g.-194-195insGAGGG 17.4 19.31

19.42


19.73

DDX58 g.-86A>C 22.6 20.51

26.92

DDX58 g.-1309A>C 22.61

19.31

26.92


36.62

34.83

152

Table 4.15. Calculated p- and q-values for HAMP, DDX58, CD163 and CD169 polymorphisms in pigs diagnosed with different viral pathogens.




Genotype PCV2

(n = 84)

PRRSV

(n = 69)

p-value q-value p-value q-value

CD163 g.2552A>G 0.0643 0.0202 0.0119 0.0298

CD169 g.1654C>A 0.2480 0.0468 0.4819 0.0644

HAMP haplotype 1 0.4934 0.0607 0.4108 0.0604

HAMP g.-947T>C 0.0364 0.0156 0.2440 0.0587

HAMP g.-1405C>G 0.0386 0.0157 0.2671 0.0591

HAMP g.-1421G>C 0.0430 0.0157 0.2671 0.0591

HAMP haplotype 2A 0.0057 0.0125 0.1450 0.0564

HAMP g.-271G>A 0.5383 0.0623 0.3349 0.0597

HAMP g.-902G>C 0.0325 0.0155 0.0340 0.0425

DDX58 g.-1748-1751delGAGA 0.3788 0.0556 0.1014 0.0540

DDX58 g.-219G>T 0.5364 0.0622 0.5996 0.0788

DDX58 g.-309G>A 0.0169 0.0148 0.4821 0.0644

DDX58 g.-293T>G 0.2112 0.0433 0.1741 0.0573

DDX58 g.-817G>A 0.5125 0.0614 0.3218 0.0596

DDX58 g.-194-195insGAGGG 0.3890 0.0562 0.3975 0.0603

DDX58 haplotype 1 0.5448 0.0630 0.3923 0.0602

DDX58 g.-86A>C 0.3939 0.0564 0.2623 0.0590

DDX58 g.-1309A>C 0.2990 0.0508 0.2651 0.0590

DDX58 haplotype 2 0.1922 0.0413 0.3116 0.0595

153

Table 4.16. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169 polymorphisms in purebred pigs.

Comparison of the percentage of animals with at least one variant allele between purebred pig breeds. 1,2,3 etc. represent number of animals with a miss call

for that SNP in that group (e.g. in the Duroc group, HAMP haplotype 1A had 1 miscall meaning the number of data points is = 102 − 1 or 101). * Difference

in % variant positive compared between all breeds using a Chi-square test (five columns two rows). Bolded text indicates a significant difference at p < 0.05.

Genotype Duroc

(n = 102)

Hampshire

(n = 100)

Landrace

(n = 100)

Large White

(n = 100)

Pietrain

(n = 73) p-value

*

CD163 g.2552A>G 38.2 14.11 7.0 27.0 28.8 < 0.0001

CD169 g.1654C>A 40.2 58.61 84.0 66.0 80.8 < 0.0001


1 2.0 8.0 9.6 < 0.0001

HAMP g.-947T>C 13.7 21.21 58.0 43.4

1 35.6 < 0.0001

HAMP g.-1405C>G 12.7 17.21 58.0 43.4

1 35.6 < 0.0001

HAMP g.-1421G>C 12.7 17.21 58.0 43.4

1 35.6 < 0.0001


1 65.0 52.0 19.4

1 < 0.0001

HAMP g.-271G>A 22.5 35.41 69.0 64.0 84.9 < 0.0001

HAMP g.-902C>G 6.9 8.11 19.0 6.0 2.7 0.0014

DDX58 g.-1748-1751delGAGA 83.3 81.81 88.0 79.0 91.8 0.1468

DDX58 g.-219T>G 1.0 0.01 0.0 2.0 1.4 0.4688

DDX58 g.-309G>A 62.41 57.6

1 24.0 55.0 57.5 < 0.0001

DDX58 g.-293T>G 25.5 32.31 51.0 58.0 39.7 < 0.0001

DDX58 g.-817G>A 13.7 4.01 26.0 17.0 17.8 0.0008

DDX58 g.-194-195insGAGGG 13.7 4.01 26.0 17.0 17.8 0.0008

DDX58 haplotype 1 13.7 4.01 26.0 17.0 17.8 0.0008

DDX58 g.-86A>C 41.2 28.31 8.0 14.0 15.1 < 0.0001

DDX58 g.-1309A>C 41.2 28.31 8.0 14.0 15.1 < 0.0001

DDX58 haplotype 2 16.7 32.31 28.0 44.0 24.7 0.0006

154

Table 4.17. p-values for pair-wise comparisons of HAMP, DDX58, CD163 and CD169

polymorphism variant genotype frequencies in purebred pigs.

The p-values indicate the statistical significance between the comparisons of the percentage

of animals with at least one variant allele between different pig breeds as assessed using a

Yates chi-square test. * indicates analyses where a one-tailed Fisher's exact probability test

was used instead of the chi-square test. Bolded text indicates a significant difference at p <

0.05. LR = Landrace; LW = Large white.

CD163 g.2552A>G Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0002 < 0.0001 0.1206 0.2542

Hampshire N/A 0.1594 0.0388 0.0305

LR N/A 0.0003 0.0003

LW N/A 0.9203

Pietrain N/A

CD169 g.1654C>A Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0137 < 0.0001 0.0004 < 0.0001

Hampshire N/A 0.0001 0.3510 0.0034

LR N/A 0.0055 0.7290

LW N/A 0.0480

Pietrain N/A

HAMP haplotype 1 Duroc Hampshire LR LW Pietrain

Duroc N/A < 0.0001 < 0.0001 < 0.0001 < 0.0001

Hampshire N/A 0.0068 0.3428 0.6315

LR N/A 0.1049 0.0307*

LW N/A 0.9203

Pietrain N/A

HAMP g.-947T>C Duroc Hampshire LR LW Pietrain

Duroc N/A 0.2253 < 0.0001 < 0.0001 0.0013

Hampshire N/A < 0.0001 0.0014 0.0547

LR N/A 0.0557 0.0059

LW N/A 0.3802

Pietrain N/A

HAMP g.-1405C>G

HAMP g.-1421G>C Duroc Hampshire LR LW Pietrain

Duroc N/A 0.4930 < 0.0001 < 0.0001 0.0007

Hampshire N/A < 0.0001 0.0001 0.0098

LR N/A 0.0557 0.0059

LW N/A 0.3802

Pietrain N/A

HAMP haplotype 2A Duroc Hampshire LR LW Pietrain

Duroc N/A 0.5839 0.9203 0.1371 < 0.0001

Hampshire N/A 0.4310 0.4274 < 0.0001

LR N/A 0.0848 < 0.0001

LW N/A < 0.0001

Pietrain N/A

HAMP g.-271G>A Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0648 < 0.0001 < 0.0001 < 0.0001

Hampshire N/A < 0.0001 < 0.0001 < 0.0001

LR N/A 0.5485 0.0255

LW N/A 0.0039

Pietrain N/A

155

Table 4.17 continued.

HAMP g.-902C>G Duroc Hampshire LR LW Pietrain

Duroc N/A 1.0000 0.0181 1.0000 0.1942*

Hampshire N/A 0.0411 0.7642 0.1237*

LR N/A 0.0103 0.0027

LW N/A 0.2657*

Pietrain N/A

DDX58 g.-1748-1751delGAGA Duroc Hampshire LR LW Pietrain

Duroc N/A 0.9203 0.4543 0.5430 0.1604

Hampshire N/A 0.3078 0.7518 0.1010

LR N/A 0.1277 0.5777

LW N/A 0.0379

Pietrain N/A

DDX58 g.-219T>G Duroc Hampshire LR LW Pietrain

Duroc N/A 0.5075* 0.5050 * 0.4925* 0.6617*

Hampshire N/A 1.0000 * 0.2513* 0.4244*

LR N/A 0.2487* 0.4220*

LW N/A 0.6168*

Pietrain N/A

DDX58 g.-293T>G Duroc Hampshire LR LW Pietrain

Duroc N/A 0.3623 0.0003 < 0.0001 0.0664

Hampshire N/A 0.0115 0.0005 0.3994

LR N/A 0.3929 0.1884

LW N/A 0.0264

Pietrain N/A

DDX58 g.-309G>A Duroc Hampshire LR LW Pietrain

Duroc N/A 0.5839 < 0.0001 0.3594 0.6242

Hampshire N/A < 0.0001 0.8231 0.8875

LR N/A < 0.0001 < 0.0001

LW N/A 0.8625

Pietrain N/A

DDX58 haplotype 1

DDX58 g.-817G>A

DDX58 g.-194-195insGAGGG

Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0311 0.0442 0.6547 0.5967

Hampshire N/A < 0.0001 0.0061 0.0063

LR N/A 0.1681 0.2753

LW N/A 1.0000

Pietrain N/A

DDX58 g.-86A>C

DDX58 g.-1309A>C Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0769 < 0.0001 < 0.0001 0.0004

Hampshire N/A 0.0004 0.0217 0.0629

LR N/A 0.2579 0.2222

LW N/A 1.0000

Pietrain N/A

DDX58 haplotype 2 Duroc Hampshire LR LW Pietrain

Duroc N/A 0.0155 0.0773 < 0.0001 0.2655

Hampshire N/A 0.6101 0.1213 0.3566

LR N/A 0.0272 0.7518

LW N/A 0.0139

Pietrain N/A

156

Table 4.18. Frequency of variant positive genotypes for HAMP, DDX58, CD163 and CD169 polymorphisms in weighted cross bred pig populations.

Comparison of the percentage of animals with at least one variant allele between the healthy reference population and different weighted cross bred pig

populations. 1,2,3 etc. represent number of animals with a miss call for that SNP in that group (e.g. in the healthy control group, DDX58 g.-309G>A had 2

miscalls meaning the number of data points is = 500 −2 or 498). LW = Large white.

Genotype

Healthy

market pigs

(n = 500)

Healthy

purebred

(n = 475)

50 % Duroc

25 % LW

25 % Landrace

50 % Landrace

25 % LW

25 % Duroc

50 % LW

25 % Landrace

25 % Duroc

33 % LW

33 % Landrace

33 % Duroc

CD163 g.2552A>G 39.8 22.81

27.6 19.8 24.8 23.8

CD169 g.1654C>A 76.4 65.01

57.6 68.5 64.0 62.8


26.3 14.9 16.4 19.0

HAMP g.-947T>C 23.8 34.22

32.2 43.3 39.6 38.0

HAMP g.-1405C>G 23.4 33.22

31.7 43.0 39.4 37.7

HAMP g.-1421G>C 23.4 33.22

31.7 43.0 39.4 37.7


60.9 61.3 58.1 59.5

HAMP g.-271G>A 71.2 53.41

44.5 56.1 54.9 51.3

HAMP g.-902C>G 8.2 8.91

9.7 12.7 9.5 10.5

DDX58 g.-1748-1751delGAGA 87.2 84.41

83.4 84.6 82.3 82.6

DDX58 g.-219T>G 0.8 0.81

1.0 0.7 1.2 1.0

DDX58 g.-309G>A 51.82

51.02

50.9 41.3 49.1 46.7

DDX58 g.-293T>G 44.6 41.41

40.0 46.4 48.1 44.4

DDX58 g.-817G>A 17.81

15.61

17.6 20.7 18.4 18.7

DDX58 g.-194-195insGAGGG 17.4 15.61

17.6 20.7 18.4 18.7


17.6 20.7 18.4 18.7

DDX58 g.-86A>C 22.6 21.71

26.1 17.8 19.3 20.8

DDX58 g.-1309A>C 22.61

21.71

26.1 17.8 19.3 20.8


29.31

26.3 29.2 33.2 29.3

157

Figure 4.2. Correlation of semi-quantitative real-time RT-PCR and microarray mRNA expression of DDX58.

R2 = correlation coefficient.

158

Figure 4.3. Correlation of DDX58 mRNA expression levels when measured using two different microarray probes.


159

Figure 4.4. Correlation of HAMP mRNA expression levels when measured using two different microarray probes.


160

DISCUSSION

In this study, we identified a large number of novel SNPs, insertions and deletions in the 5'-

promoter regions of the HAMP and DDX58 genes of healthy market weight pigs. These

polymorphisms were identified in a group of pigs that exhibited marked variation in mRNA

expression of these genes as measured by microarray (Chapter 2). Some HAMP SNPs (n = 3) were

more frequent in pigs with increased relative mRNA expression; others (n = 2) with decreased

relative hepatic expression. Additionally five polymorphic variants in DDX58 were more frequent in

pigs with decreased hepatic expression of DDX58 mRNA.

At present, little is known about the antimicrobial properties of hepcidin, the protein product

of the HAMP gene (Badial et al. 2011, Fry et al. 2004, Krause et al. 2000, Sang et al. 2006). HAMP

mRNA expression is increased during inflammation and some bacterial infections and, as a result,

hepcidin has been classified as a type II acute-phase protein (Hocquellet et al. 2012, Nemeth et al.

2003, Sang et al. 2006). A synthetic human peptide, Hepc25, has been shown to be active against both

Gram-positive and Gram-negative bacteria but, unlike other cationic AMPs, this antibacterial activity

is not dependent on disruption of the cell membrane and the exact mechanism remains unclear

(Hocquellet et al. 2012). In other studies, increased levels of hepcidin were linked to the inhibition of

iron absorption in the small intestine and the uptake of iron by tissue macrophages sequestering its

availability from bacterial pathogens (Nemeth et al. 2003). We found no evidence of inflammation,

clinical disease or an increase in acute phase mRNA expression in any of our healthy market weight

pigs, including the pigs with high levels of HAMP mRNA. This suggests that the mRNA variations

observed in our study were due to naturally-occurring differences in constitutive gene expression

rather than the changes in response to inflammation or disease.

A number of SNPs and deletions have been identified within both coding and non-coding

regions of the human HAMP gene and these polymorphisms have been linked to clinical iron overload

disorders (Matthes et al. 2004, Nemeth et al. 2006, Roetto and Camaschella 2005). Polymorphisms

have also been detected in the promoter region of the human gene but these variations did not affect

161

mRNA expression. Instead, they resulted in the generation of a new start codon (ATG) at position -25

(g.-25G>A) and the production of an abnormal protein. In contrast, some of the porcine SNPs

identified in our study were more frequent in pigs with either decreased or increased HAMP

expression, suggesting that these SNPs impact the transcriptional regulation of HAMP. These findings

pave the way for additional studies to better define the role of these SNPs in the regulation of HAMP

expression. As highlighted by the difficulties we encountered during the development of RT-PCR,

assays for the quantification of HAMP mRNA will need to be carefully designed to ensure they

quantify all known transcripts of the gene. Our results provide the rationale and baseline for further

development of these porcine-specific assays.

In this study the HAMP g.-902C>G SNP was one of the polymorphisms associated with

decreased microarray expression, although not statistically significantly so. This SNP was

significantly more frequent in the infectious and pneumonia disease groups with significant increases

also identified with Mycoplasma spp. and PCV2 pathogen groups. Mycoplasma spp. do not contain

bacterial cell membranes and, although there is no reported evidence of hepcidin antimycoplasmal

activity, some antimicrobial peptides have been shown to have inhibitory effects against this group of

pathogens (Nir-Paz et al. 2002). Additionally, as mentioned above, the antibacterial mechanism of

hepcidin appears to be independent of bacterial membrane disruption (Hocquellet et al. 2012). The

HAMP g.-902C>G SNP was also increased in frequency in the PRRSV group and trended towards

statistical significance; genotyping additional pigs may be useful in clarifying this association. In

contrast the variant HAMP haplotype 2A alleles were significantly lower in the infectious, pneumonia

and septicemia disease groups and significantly less frequent in the PCV2 pathogen group while the

three SNPs that were significantly associated with increased hepatic gene expression, HAMP g.-

947T>C, HAMP g.-1405C>G and HAMP g.-1421G>C were also significantly less frequent in the

PCV2 pathogen group. The reason for the associations observed between these polymorphisms in a

cationic antibacterial peptide and viral pathogens such as PCV2 and PRRSV is not directly evident

and the most likely explanation is that it may be linked to a functionally significant mutation

somewhere else, either on the same chromosome or within other genes of the porcine genome that

162

may play an important role in antiviral functions. Recent evidence has shown direct antiviral functions

of human hepcidin against hepatitis C virus (HCV) in cultured cells and supports the potential for

porcine hepcidin to exhibit similar antiviral activity against viral pathogens in pigs (Bartolomei et al.

2011, Liu et al. 2012). HAMP haplotype 1A was also approximately eight times less frequent in the

K88+ E. coli pathogen group suggesting a protective phenotype associated with this variant haplotype

combination. Although in this study the majority of pigs included in the K88+ E. coli pathogen group

were from unrelated farms (68 %; n = 21/31), care should be taken with this interpretation as some of

the diseased E. coli submissions may be from the same litter which may have underrepresented this

specific SNP haplotype. Larger numbers are needed to better assess the biological and clinical

significance of hepcidin expression and the role of promoter polymorphisms plays in such disease

susceptibility.

To our knowledge, this is the first study to detect polymorphisms in the promoter region of

DDX58. This gene, which is located on Sus scrofa chromosome 10 (Zhang et al. 2000), codes for

RIG-1, a pattern recognition receptor that is widely distributed in tissues including, but not limited to,

the kidney, liver, muscle, testis and thymus (Lech et al. 2010). Using microarray technology and DNA

sequencing, we identified 19 polymorphisms in the promoter region of DDX58, five of which were

more frequent in pigs with a decrease in constitutive gene expression with three of these being

statistically significant (DDX58 haplotype 2). Some of the five polymorphisms were also present in

pigs with higher levels of DDX58 mRNA, but at a reduced frequency relative to pigs with low levels

expression (Table 4.6 and 4.7).

In another recent study, Kojima-Shibata et al (2009) identified seventeen SNPs in the coding

region of the porcine DDX58 gene including six non-synonymous SNPs, four of which are proposed

to result in structural changes that may affected ligand binding and signalling via RIG-1 (Kojima-

Shibata et al. 2009). Numerous SNPs, including seven non-synonymous SNPs, have also been

described in coding regions of the human DDX58 gene. Based on biochemical and structural

modeling, two of these SNPs were flagged as having an adverse effect on RIG-1 binding and

signaling (Pothlichet et al. 2009). One of the variants was a frame shift mutation (P(229)fs) that

163

generated a truncated receptor that resulted in exaggerated signalling. The second resulted in a serine

to isoleucine (S(183)I) substitution that alters the structure of the second CARD domain of RIG-1 and

interferes with CARD-mediated antiviral signalling. Another study reported two additional amino

acid substitutions, T(55)I and K(172)R located in the first and second CARD domains, that have been

shown to have a detrimental effect on RIG-1/IPS-1 interactions (Gack et al. 2008). Other studies have

reported that RIG-1-/-

knockout mice are more susceptible to viral infections ((Kato et al. 2006). This

high degree of polymorphism within the DDX58 gene may suggest that variation may increase the

range of ligand recognition increasing the ability to recognise a large variety of pathogens and may

have evolved as a result of strong selective pressure. In contrast a high level of redundancy between

different innate immune factors may allow polymorphisms to accumulate as a result of genetic drift.

The central role that DDX58 plays in antiviral signalling and the adverse effects associated with

mutations and loss of this innate immune factor in knockout mouse studies would suggest that

redundancy and genetic drift is less likely (Kato et al. 2006, Pothlichet et al. 2009).

In this study, we identified five promoter polymorphisms that were more frequent in pigs with

a relative decrease in DDX58 mRNA expression. When interpreted in the context of the above studies,

it suggests that pigs with low level expression of DDX58 may be at increased risk of acquiring

PPRSV and other viral and infectious diseases and that selective breeding for pigs with higher levels

of DDX58/RIG-1 will result in improved resistance to these diseases. Of these five promoter variants,

significant disease associations were identified for all variants except the DDX58 g.-542C>T SNP for

which MALDI-TOF mass spectrometry SNP genotyping failed. The first of these, DDX58 g.-293T>G

SNP was significantly more frequent in the infectious, septicemia and S. Typhimurium groups while

DDX58 haplotype 2 was more frequent in individuals diagnosed with H. parasuis.

In this study additional associations were also identified in gene variants not associated with

altered constitutive hepatic gene expression. The DDX58 g.-309G>A was significantly less frequent

in the infectious, enteric and pneumonia disease groups as well as the K88+ E. coli and PCV2

pathogen groups. DDX58 g.-1748-1751delGAGA as well as the DDX58 g.-86A>C and DDX58 g.-

1309A>C variants were less frequent in the H. parasuis and K88+ E. coli pathogen group respectively

164

suggesting a protective phenotype. In contrast the DDX58 g.-817G>A, DDX58 g.-194-195insGAGGG

and DDX58 haplotype 1 were more frequent in both the K88+ E. coli and S. Typhimurium pathogen

groups. As mentioned for the HAMP promoter variants present at decreased frequencies in the E. coli

pathogen group, care should be taken in cases of artifactual over or under representation of the

DDX58 promoter variants in this group. Concomitant associations with other enteric pathogens such

as S. Typhimurium in the case of DDX58 g.-817G>A, DDX58 g.-194-195insGAGGG and DDX58

haplotype 1 however further supports the significance of these associations.

It is interesting to note that despite the critical role RIG-1 plays as an antiviral sensor across

species, only a single association between PCV2 (A allele of DDX58 g.-309G>A was significantly

less frequent in this disease group), and no associations with PRRSV were identified in the current

study. In pigs, RIG-1 is induced following infection with porcine reproductive and respiratory

syndrome virus (PRRSV) and this induction has been proposed to be essential for combating PRRSV

(Zhang et al. 2000). Other studies, however, have also reported an inhibitory effect of PRRSV

infection on RIG-1 signaling through inactivation of the IPS-1 adapter molecule (Luo et al. 2008, Zhu

et al. 2012). Although decreased constitutive production of RIG-1 in association with promoter

polymorphisms may further impair antiviral innate responses to PRRSV, independent inhibition of the

downstream adaptor IPS-1, as reported by Luo et al. and Zhu et al., perhaps plays a more significant

role regardless of the level of DDX58 expression.

Recently certain CD169 and CD163 SNP genotypes have been associated with PRRSV

resistance (Ren et al. 2012). CD169 g.1654C>A is a non-synonymous SNP resulting in a Leu552Ile

substitution and is situated in the region encoding the immunoglobulin C-2 type (IGc2) domain. This

domain is associated with the formation of a disulfide bond that may be critical for the native

conformation and stability of the protein and may impair the effective adhesion and subsequent

endocytosis of PRRSV (Ren et al. 2012). CD163 g.2552A>G, also a non-synonymous SNP that

results in a Lys851Arg substitution, in turn is situated in the region encoding the eighth scavenger

receptor domain of CD163 (Ren et al. 2012). This domain contains six conserved cysteine residues

that act as bacterial antigen binding sites; however it is unclear how these binding sites are proposed

165

to interact with PRRSV. In this study we assessed the frequencies of these identified SNPs in North

American pigs and looked to determine if similar associations with PRRSV existed in these pigs. The

CD163 g.2552A>G SNP was present in all North American pig breeds and the A allele was also

significantly associated with a decreased risk of PRRSV infection in North American pigs. The G

allele of this SNP was also more frequent in most disease groups and all remaining pathogen groups.

Infectious diseases in pigs are often caused by a variety of concomitant viral and bacterial infections

and this broad association with infectious diseases may indeed reflect this multifactorial nature. In

comparison the variant genotype frequency (A allele) of the CD169 g.1654C>A SNP did not vary

significantly between different breeds, disease groups and most pathogens and was only

approximately 1.2 times more frequent in the K88+ E. coli pathogen group. The exact reason for this

lack of association is not clear and perhaps genotyping larger populations of both healthy and diseased

pigs exposed to PRRSV may result in the identification of similar associations as observed in

commercial crossbred pigs in China.

To date, very few SNPs have been described in the genes coding for mammalian PGLYRPs.

A single non-synonymous SNP, C(419)A, has been reported in the coding region of human PGLYRP2

gene (Dziarski and Gupta 2010, Wang et al. 2003). The SNP, which involves the replacement of a

highly conserved cysteine with an alanine residue, disrupts the amidase activity of this PGRP (Wang

et al. 2003). No SNPs have been identified in 5'-promoter region of the bovine PGLYRP1 gene,

however two synonymous coding region SNPs [c.102G>C, c.480G>A] and a single 3'UTR SNP

[c.625C>A], were identified in the bovine PGLYRP1 gene (Pant et al. 2011). The c.480G>A SNP was

associated with a marginally increased risk in Mycobacterium avium (subsp. paratuberculosis)

infection. In the current study, no polymorphisms were detected in the 5'-upstream promoter regions

of the porcine PGLYRP1 and PGLYRP2 genes, despite significant variation in constitutive hepatic

expression. However, our sequencing studies were limited to include 1,332 and 787 bp of the 5'-

upstream promoter region of the PGLYRP1 and PGLYRP2 genes respectively. The remaining regions

of the 5'-UTRs as well as other non-coding and coding regions are still to be characterized and may

contain polymorphisms that alter the expression of these genes. It is also known that the pig genome

166

contains two splice variants of PGLYRP2 that may be regulated by different transcriptional control

mechanisms (Sang et al. 2005). The long isoform is predominantly expressed within the liver while

the short isoform is expressed in a variety of tissues including the bone marrow, intestine, spleen, and

kidney as well as the liver (Li et al. 2006, Sang et al. 2005). Alignment of our microarray probes with

sequences available in the Ensembl online genome browser indicated that one of the probes aligned

with both the long [ENSSSCT00000022764] and short [ENSSSCT00000023031] (Flicek et al. 2013)

isoforms of PGLYRP2, whereas the second probe aligned with only the long isoform. Thus,

differential expression of these transcript variants could also contribute to observed variation in

PGLYRP2 mRNA levels in different pigs. PGLYRP1 is abundantly expressed in polymorphonuclear

granulocytes and upon degranulation localize in neutrophil extracellular traps (NETs) where they play

an essential role in neutrophil-mediated bacterial killing (Cho et al. 2005, Dziarski and Gupta 2010,

Tydell et al. 2006). Thus, differences in the relative number of circulating granulocytes and in blood

flow to different lobes of the liver that may have been sampled might have contribute to observed

variations in PGLYRP1 mRNA levels in healthy pigs.

Although relatively large segments of the promoter regions of these four genes were

sequenced in this study and a large number of polymorphisms were identified for some of these genes,

further sequencing of the 5'-UTRs as well as other coding and non-coding regions of these genes may

result in the detection of additional disease-conferring polymorphisms that alter mRNA expression

and protein function. Increasing the sample size and screening additional pigs may also further expand

the identification of additional genetic markers and will be valuable to strengthen the observations of

this study. The continued refinement of RT-PCR assays will be needed to further validate the

observed associations with altered gene expression of both HAMP and DDX58 and to clarify

discrepancies noted for DDX58 expression. The genetic variations detected in HAMP and DDX58

may represent a valuable set of markers for assessing disease susceptibility in pigs and represents an

important step in developing a genetic selection panel that can be used to increase disease resistance

in the commercial swine population.

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GENERAL DISCUSSION

The original objective of this research was to identify porcine innate immune genes with

substantially increased, or decreased, constitutive gene expression in healthy pigs. Further

investigation was then aimed at whether or not any observed changes in expression could be attributed

to underlying genetic variations within proposed regions of transcriptional regulation or control.

Finally disease- and breed-association studies were used to evaluate their potential impact on disease

resistance or susceptibility. The study was based on the premise that this information could become

useful in selective breeding of pigs with enhanced innate resistance to common infectious diseases

that have an adverse effect on commercial swine production.

The majority of porcine microarray studies to date have aimed at identify differentially

expressed genes following experimental or natural infection with a limited number of pathogens (Bao

et al. 2012, Fernandes et al. 2012, Gladue et al. 2010, Hedegaard et al. 2007, Lee et al. 2010, Li et al.

2010, Li et al. 2013, Ma et al. 2012, Mortensen et al. 2011, Moser et al. 2004, Moser et al. 2008,

Sanz-Santos et al. 2011, Skovgaard et al. 2010, Tomas et al. 2010, Wysocki et al. 2012, Zuo et al.

2013). Other studies have also evaluated differential expression patterns among different

physiological states (Jensen et al. 2012, Ostrup et al. 2010, Shu et al. 2012). The contribution of these

studies to our knowledge of the porcine transcriptome serve as a valuable resource however does not

provide insight on the constitutive expression of the genes of the innate immune system. A single

recent microarray experiment by Freeman et al. was the first to attempt to establish a porcine gene

expression atlas and evaluated the expression profiles of 62 different tissue/cell types (Freeman et al.

2012). This study was however limited to four pigs and does not address the potential of variation in

constitutive gene expression between individuals. Therefore, to my knowledge, this is the first study

to use whole genome microarray technology specifically focussed on measuring the constitutive

expression of innate immune genes in the liver of healthy pigs to identify innate immune genes that

exhibit marked variation in constitutive gene expression. This study is also unique in the fact that

similar focussed studies have not been performed in any other tissue or species.

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A large number of genes proposed to play a role in innate immune defense exhibited widely

variable constitutive gene expression. One of the identified genes, MBL2, has previously been studied

and an association between two specific promoter polymorphisms, the MBL2 g.-1091G>A and MBL2

g.-261C>T SNPs, and reduced hepatic gene expression was identified (Lillie et al. 2007). Microarray

and genotyping analysis indicated that both of these polymorphisms were also associated with

decreased hepatic expression of MBL2 in this microarray study. The high degree of concordance

between these two studies supports my hypothesis that microarray technology in combination with

sequencing can be used to identify novel polymorphisms (SNPs, insertions, deletions) associated with

altered expression of innate immune genes. These initial proof-of-concept studies pave the way for

additional investigations aimed at identifying genetic mutations (SNPs, insertions, deletions) that are

responsible for the alterations observed in the expression of other variably expressed innate immune

genes identified in this study. An understanding of these defects is likely to prove valuable in the

development of improved strategies for the prevention and control of infectious disease. Applying

these same techniques in other immunologically important tissues may lead to the identification of

additional variably expressed innate immune genes that can be included in future investigations.

Additionally the opportunity exists to apply the same validated methods of this study, and perhaps our

microarray dataset as a starting point, to evaluate the constitutive gene expression of other groups or

sets of genes that may affect economically important traits. For example, such investigations could be

aimed at other tissues with a focus on genes involved in metabolism, fertility and/or other recognised

and important production characteristics. The continued refinement and especially improvement of

gene annotation of porcine specific microarray platforms will be essential for the success of such

future studies.

In chapter 3 and 4, I further expanded the investigations of some of these genes, SCGB1A1,

SFTPD, HAMP, DDX58, PGLYRP1 and PGLYRP2, that exhibited the widest variation in hepatic gene

expression when analyzed by microarray technology and for which no previous investigation had

been attempted. Further characterization of the promoter regions of these genes resulted in the

identification of a large number of novel polymorphisms, including single nucleotide polymorphisms,

insertions and deletions in the 5'-upstream promoter regions of SCGB1A1, SFTPD, HAMP and

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DDX58; some of which were more prevalent in pigs with increased or decreased mRNA expression.

No polymorphisms were identified in the genes encoding PGLYRP1 and PGLYRP2 and other causes

for variation in expression of these genes should be sought.

A particularly interesting and unexpected finding of these investigations is that of a potential

second gene copy for the porcine SCGB1A1 gene and the association between this variant sequence

and increased hepatic SCGB1A1 expression. Hepatic expression of this gene could not be confirmed

in previous studies however the present study confirmed hepatic expression of this gene using both

microarray and RT-PCR techniques. A possible reason for these discrepancies with previous studies

may lie in the techniques used; with RT-PCR and microarray expression being regarded as more

sensitive techniques as compared to northern blot analysis (Gutierrez Sagal and Nieto 1998). Further

investigation is warranted, and the careful design of PCR assays able to discern between the two

distinct SCGB1A1 sequences may be helpful to further confirm the existence of two distinct

SCGB1A1 gene copies in the pig. Further evaluation of the biological and functional significance of

these two different SCBG1A1 sequences within the liver, lung and other tissues is necessary to further

understand the role this immunomodulatory protein may play within the porcine innate immune

system. In the present study the identified genetic variants were also associated with increased

constitutive hepatic gene expression. It remains to be determined whether or not a relative increase in

expression results in increased functional protein. Disease association studies of SCGB1A1 genotypes

could not be assessed with the other innate immune polymorphisms identified in this study and the

consequences of increased gene expression in light of inflammation and disease susceptibility or

resistance is still unknown.

Using MALDI-TOF mass spectrometry SNP genotyping I compared the variant genotype

frequencies for all characterized promoter polymorphisms, including those associated with variable

hepatic gene expression, between a population of healthy market weight pigs (n = 500) and pigs that

were submitted for autopsy evaluation and that have been diagnosed with a variety of disease

syndromes and pathogens (n = 386). A number of disease and pathogen group associations were

identified for a number of HAMP and DDX58 polymorphisms and are discussed in detail in Chapter 3

170

and 4. Except for the SFTPD SNPs, significant disease associations were identified for all

polymorphisms and polymorphic haplotypes that were more frequent in pigs with either increased or

decreased mRNA expression and that could be evaluated using MALDI-TOF genotyping.

Only three statistically significant associations were identified between specific

polymorphisms and increased (HAMP haplotype 4 and SFTPD g.-4509A>G) or decreased (DDX58

haplotype 2) constitutive gene expression respectively. Due to low sample numbers, the effect of the

identified polymorphisms on gene expression needs further clarification, especially in cases were only

heterozygous individuals or few homozygous variant individuals were identified. The identification of

significant disease associations for these polymorphisms does however suggest that these

polymorphisms may indeed significantly impact gene expression. Along with significant disease

associations, the relative scarcity of homozygous variant individuals may also point to a markedly

detrimental phenotype for some of these identified promoter polymorphisms including CD163

g.2552A>G; HAMP haplotype 1A; HAMP g.-947T>C; HAMP g.-1405C>G; HAMP g.-1421G>C;

HAMP haplotype 2A; HAMP g.-902C>G; DDX58 g.-219T>G; DDX58 g.-309G>A; DDX58 g.-

293T>G; DDX58 g.-817G>A; DDX58 g.-194-195insGAGGG; DDX58 haplotype 1; DDX58 g.-

86A>C; DDX58 g.-1309A>C; DDX58 haplotype 2 and SFTPD g.-4509A>G. It may be the case that

selective pressure may have resulted in the progressive elimination of such detrimental genotypes

from the population.

All three SFTPD promoter SNPs were found only in pigs with high relative SFTPD

expression with the SFTPD g.-4509A>G SNP being statistically significantly so. Because of the

established role this lectin plays in innate pulmonary defense (Haagsman et al. 2008, Hartl and Griese

2006), I originally hypothesized that increased expression of SFTPD would result in a beneficial

phenotype to infectious disease, especially with regard to pulmonary pathogens. In this study however

the variant G allele of SFTPD g.-4509A>G, although not statistically so, was increased two- to four-

fold in pigs diagnosed with pathogens playing a role in pulmonary disease, including Haemophilus

parasuis, Mycoplasma spp., PCV2 and PRRSV and a protective effect was therefore not observed. As

a result of tissue specific transcription factors such as NFAT and TTF-1 in the lung, the regulation of

171

expression of pulmonary and hepatic SFTPD may differ. Whether or not the identified

polymorphisms in this study would affect these specific transcription factor binding sites in the lung

will need further investigation. SP-D has been shown to have a regulatory role in pulmonary

inflammation and SFTPD-/-

mice challenged with intraperitoneal injection of lipopolysaccharide (LPS)

showed better survival rates than wild type mice (King and Kingma 2011). As an alternative it should

therefore also be considered that enhanced expression of SFTPD may in fact be detrimental and may

result in excessive inflammation and local tissue damage thereby increasing disease morbidity.

It is interesting to note that a number of HAMP SNPs, including those associated with

alterations in gene expression, had significant associations in the viral disease groups, an unexpected

finding for hepcidin as a cationic antimicrobial peptide (Krause et al. 2000). This may indicate the

existence of a linked functionally significant mutation somewhere else within antiviral components of

the innate immune genome. Interestingly human hepcidin has recently been shown to have direct

antiviral activity against hepatitis C virus (HCV) in infected cell cultures (Bartolomei et al. 2011, Liu

et al. 2012). Therefore the associations observed between specific HAMP SNPs and viral diseases in

this study may perhaps indicates a similar role for hepcidin in the defense against viral pathogens in

pigs. Alternatively it should also be considered that this may be the result of co-infection between

bacterial and viral pathogens, which is a common occurrence in many porcine disease syndromes.

Some discrepant results were also seen with identified DDX58 SNPs. RIG-1, the protein

product of this gene, is considered an essential component of the antiviral innate immune response

(Kato et al. 2006, Schlee et al. 2009, Wilkins and Gale 2010, Yoneyama et al. 2005). Despite this

critical role only a single statistically significant viral (PCV2) disease association was identified in

this study. This discrepancy may suggest an effective evasion mechanism inherent to the specific viral

pathogens tested. This does appear to be a possibility for PRRSV, which has been shown to have an

inhibitory effect on RIG-1 signaling by inactivation IPS-1, a downstream adapter molecule involved

in RIG-1 signaling (Luo et al. 2008, Zhu et al. 2012). Similar mechanisms have however not been

identified for PCV2. Increasing sample size and testing other viral pathogens in pigs may identify

additional associations.

172

Additionally in Chapter 4, genotype frequencies of two additional SNPs, within the genes

encoding for the CD163 and CD169 macrophage receptors, were also investigated. Both these

receptors act as essential PRRSV receptors and specific SNP genotypes have been associated with

PRRSV resistance in commercial pigs in China (Ren et al. 2012). These SNPs have not been

evaluated in the North American pig population. This study aimed to investigate if these SNPs also

existed within this population and if similar associations with PRRSV resistance could be identified in

North American pigs. As observed in Chinese pigs the G allele of CD163 g.2552A>G SNP was

significantly more frequent in pigs diagnosed with PRRSV however similar associations were not

identified for the A allele of CD169 g.1654C>A SNP. Increased sample size and carefully designed

infection trials may prove useful for further evaluation of these SNPs and the pathogenesis they play

in PRRSV resistance before they can be adopted into strategies to control PRRSV in commercial

herds, both in North America and elsewhere in the world.

In this study I focussed my search within the 5'-promoter region, upstream of the ATG start

codon, of these genes in an attempt to identify polymorphisms that may be situated within regions

important for the initiation or regulation of gene transcription. Although relatively large segments of

the promoter regions of these six genes were sequenced in this study, further sequencing of the 5'-

UTRs may result in the identification of additional polymorphisms affecting gene transcription.

Increasing the sample size and screening additional groups of diseased pigs may also further expand

the identification of other markers. Polymorphisms within regions other than the putative promoter

region have also been reported to affect expression levels of some innate immune genes, although the

exact mechanisms by which these polymorphisms affect gene transcription remain unknown (Juul-

Madsen et al. 2011, Lillie et al. 2006). Further sequencing of other coding and non-coding regions of

the innate immune genes in this study may result in the detection of such additional polymorphisms

that may affect gene transcription. Increasing sample size, especially through using DNA extracted

from formalin-fixed, paraffin embedded tissue sections may be beneficial in further evaluating

identified disease associations especially where pathogen sample sizes were low. The careful planning

of large prospective infection trials may also prove useful in determining the significance of identified

173

genetic markers. It is also imperative to evaluate these identified markers in conjunction with

important production characteristics. This will ensure that the selection of genotypes associated with

improved innate disease resistance also reflects in improved production.

In conclusion, the polymorphisms described in this thesis, together with previously identified

markers, and newly identified disease and expression variation associations form an important early

step in the development of a genetic selection strategy aimed at increasing innate disease resistance in

pigs. The ability to select for higher levels of innate disease resistance would result in increased

production, promote pig health and welfare and decrease the need for antimicrobial drugs in

commercial pig populations.

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SUMMARY AND CONCLUSIONS

1. Using whole genome transcriptome analysis we found that the constitutive hepatic expression

of a number of innate immune genes varied quite widely in healthy market weight pigs. Thirty

innate immune genes (26.3 %, n = 114) exhibited a calculated gene expression ratio of > 10

when comparing mean gene expression values of either the top 50 % to the bottom 6 % of pigs

or the mean gene expression of the top 6 % of pigs compared to the bottom 50 % of pigs.

2. As expected MBL2 was one of the most variably expressed innate immune genes. Pigs that

were homozygous for the MBL2 g.-1091G>A SNP exhibited a statistically significant decrease

in MBL2 gene expression while pigs that were heterozygous for this SNP exhibited a less

profound decrease. This confirmation of previous RT-PCR findings for this promoter SNP

indicates that promoter polymorphisms that affect gene expression can be reliably revealed by

expression microarray surveys.

3. We designed a duplex RT-PCR assay for sex-genotyping pigs; targeting the Y-encoded, testis-

specific protein (TSPY) and mitochondrial cytochrome b (MT-CYB) genes. Comparison of RT-

PCR sex-typing results and microarray mRNA expression resulted in the identification of a

sexually dimorphic expressed innate immune gene; ATP-dependent DEAD (Asp-Glu-Ala-

Asp) box polypeptide 3, Y-linked gene (DDX3Y). This duplex RT-PCR assay, as well as

microarrays containing the DDX3Y gene, can be used for accurate sex-genotyping of pigs.

4. Three novel SNPs, SFTPD g.-4509A>G; SFTPD g.-4394G>A and SFTPD g.-4350C>T, were

identified in the 2682 bp of the 5'-promoter region, upstream of the putative exon 0 of SFTPD.

We successfully designed restriction fragment length polymorphism assays to genotype pigs

for these three identified SNPs using NspI, AciI and EcoNI as restriction enzyme

175

endonucleases and all three SNPs were found to be more frequent in pigs with increased

hepatic expression.

5. We identified a novel polymorphic sequence in the 5'-upstream promoter region of the porcine

SCGB1A1 gene. This sequence was nearly identical to a second annotated SCGB1A1 gene

within the Ensembl genome browser; reportedly located 44,396 bp upstream on the reverse

strand on Sus scrofa chromosome 2 [ENSSSCT00000014276]. Our preliminary data suggests

that this sequence, which contains a 334 bp insertion and numerous other polymorphisms,

represents a second unique SCGB1A1 gene copy that is associated with high levels of mRNA

expression.

6. Fourteen novel polymorphisms were identified in a 2441 bp segment of the 5'-upstream

promoter of the HAMP gene, including four transversion SNPs, nine transition SNPs and one

deletion. Two of the four variant haplotypes, HAMP haplotype 3 and HAMP haplotype 4, were

present at an increased frequency in pigs with low or high HAMP expression respectively. The

TC/CG/GC genotype of HAMP haplotype 4 was significantly associated with increased

hepatic expression of HAMP. Comparison of allele frequencies between diseased pigs

submitted for autopsy evaluation and healthy market weight cross bred pigs identified a

number of significant disease and pathogen associations for many of these polymorphisms.

7. Nineteen novel polymorphisms were identified in a 2364 bp segment of the 5'-upstream

promoter of the DDX58 gene, including four transversion SNPs, ten transition SNPs, three

deletions and two insertions. One of the three identified polymorphic haplotypes, DDX58

haplotype 2, as well as two SNPs, DDX58 g.-293T>G and DDX58 g.-542C>T, were found to

be more frequent in pigs with low DDX58 expression. DDX58 haplotype 2 was significantly

associated with decreased hepatic expression of this gene. Comparison of allele frequencies

176

between diseased pigs submitted for autopsy evaluation and healthy market weight cross bred

pigs identified a number of significant disease and pathogen associations for many of these

polymorphisms.

8. The CD163 g.2552A>G SNP, previously associated with resistance to PRRSV infection in

commercial Chinese pigs was present in all evaluated North American pig breeds and

populations and the A allele was associated with a decreased risk of PRRSV infection in North

American pigs. In comparison the variant genotype frequency (A allele) of the CD169

g.1654C>A SNP, also previously associated with resistance to PRRSV infection, did not vary

significantly between healthy pigs and pigs infected with PRRSV.

9. No SNPs, insertions or deletions were detected in the 5'-upstream promoter and first coding

exons of PGLYRP1 and PGLYRP2. Although the reason(s) is not known, variations in the

expression of these genes may be due to polymorphisms further upstream in the promoter

regions of these genes as well as the existence of two PGLYRP2 splice variants. In addition,

the main site of expression of PGLYRP1 is within polymorphonuclear granulocytes and

variation in the circulating granulocyte pool and differences in blood flow to different liver

lobes may have contributed to the observed variation of PGLYRP1 expression.

177

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Scheffer H, Gerritsen J, Colle'e JM, Ten Kate LP, Mukherjee AB (1997) Human uteroglobin gene:

structure, subchromosomal localization, and polymorphism. DNA Cell Biol 16:73-83

Zhao ZL, Wang CF, Li QL, Ju ZH, Huang JM, Li JB, Zhong JF, Zhang JB (2012) Novel SNPs of the

mannan-binding lectin 2 gene and their association with production traits in Chinese Holsteins. Genet

Mol Res 11:3744-3754

Zheng Q, Wang XJ (2008) GOEAST: a web-based software toolkit for Gene Ontology enrichment

analysis. Nucleic Acids Res 36:W358-63

Zhou H, Hu J, Luo Y, Hickford JG (2010) Variation in the ovine C-type lectin dectin-1 gene

(CLEC7A). Dev Comp Immunol 34:246-249

Zhou H, Hickford JG, Fang Q, Lin YS (2007) Allelic variation of the ovine Toll-like receptor 4 gene.

Dev Comp Immunol 31:105-108

Zhou X, Su Z (2007) EasyGO: Gene Ontology-based annotation and functional enrichment analysis

tool for agronomical species. BMC Genomics 8:246

Zhu L, Zhou Y, Tong G (2012) Mechanisms of suppression of interferon production by porcine

reproductive and respiratory syndrome virus. Acta Virol 56:3-9

205

Zuo D, Cai X, Zhao N, Zhang L, Chen Z (2010) Location of MBL-associated serine proteases binding

motifs on human mannan-binding lectin (MBL). Protein Pept Lett 17:131-136

Zuo Z, Cui H, Li M, Peng X, Zhu L, Zhang M, Ma J, Xu Z, Gan M, Deng J, Li X, Fang J (2013)

Transcriptional Profiling of Swine Lung Tissue after Experimental Infection with Actinobacillus

pleuropneumoniae. Int J Mol Sci 14:10626-10660

206

APPENDIX I: LIST OF PREVIOUSLY IDENTIFIED INNATE IMMUNE GENE SNPS USED

FOR MALDI-TOF MASS SPECTROMETRY SNP GENOTYPING

Innate immune factor Gene symbol SNP ID

Ficolin-α FCN1 c.1139G>A

Ficolin-β FCN2 g.-134A>G

Galectin 4 LGALS4 c.96C>T

Galectin 4 LGALS4 c.587C>T

Galectin 4 LGALS4 c.928A>G

Mannan-binding lectin-A MBL1 c. 271G>T

Mannan-binding lectin-A MBL1 c. 687C>T

Mannan-binding lectin-A MBL1 g.IVS1C>T

Mannan-binding lectin serine protease 1 MASP1 c.433C>T

Mannan-binding lectin-C MBL2 g.-2158T>C

Mannan-binding lectin-C MBL2 g.-1646G>T

Mannan-binding lectin-C MBL2 g.-1091G>A

Mannan-binding lectin-C MBL2 g.-261C>T

Surfactant protein A SFTPA1 c.439G>A

Surfactant protein A SFTPA1 c.599T>A

Toll-like receptor 1 TLR1 c.2305C>T

Toll-like receptor 2 TLR2 c.406C>G

Toll-like receptor 4 TLR4 c.962G>A

Toll-like receptor 5 TLR5 c.834T>G



Nomenclature based on the human genome variation society (den Dunnen and Antonarakis 2000)

207

APPENDIX II: RANKING OF INNATE IMMUNE GENES BY VARIATION IN CONSTITUTIVE GENE EXPRESSION (TOP 6 % VS.

BOTTOM 50 %)

Genes are ranked based on the calculated gene expression ratio (GER). The GER (Log2) for each gene was calculated by comparing the mean gene expression

of the top 6 % (n = 5) of pigs to the bottom 50 % (n = 43) of pigs. Reference genes are shown in bold and underlined. Additional target genes with a

calculated GER > 10 are shown in bold. Text in parenthesis indicates Ensembl or GenBank reference sequence.

Rank GER Gene

Symbol Gene Description Rank GER

Gene

Symbol Gene Description

1 44.4 MBL2 Mannan-binding lectin C [NM_214125] 13 14.9 NLRP7 NACHT, leucine-rich repeat and PYD

containing 7 Fragment

[ENSSSCT00000003642]

2 44.0 SFTPD Surfactant protein D [NM_214110] 14 14.0 SELE Selectin E [NM_214268]

3 37.0 PR39 Peptide antibiotic PR39 [NM_214450] 15 13.7 BD108-like Pre-pro-beta-defensin 108-like

(LOC692190), mRNA

[NM_001040641]

4 37.0 DDX3Y ATP-dependent DEAD (Asp-Glu-Ala-

Asp) box polypeptide 3, Y-linked gene

[AK344932]

16 13.5 LY49 Killer cell lectin-like receptor

subfamily A, member 1 [NM_214338]


PMAP-23 [NM_001129976] 17 12.9 ZBP1 Z-DNA binding protein 1

[NM_001123216]

6 27.0 NPG4 Protegrin 4 [NM_213863] 18 12.7 PGLYRP1 Peptidoglycan recognition protein 1

[NM_001001260]

7 26.8 SCGB1A1 Secretoglobin, family 1A, member 1

(uteroglobin) [ENSSSCT00000014276] 19 12.7 LGALS12 Galectin 12 [NM_001142844]


PMAP-37 [ENSSSCT00000012426]


PMAP-36 [NM_001129965]

9 25.6 ITLN2 Intelectin 2 [NM_001128453] 21 12.4 LGALS3 Galectin 3 [NM_001142842]

10 20.9 pPGRP-S Peptidoglycan recognition protein S

[AK231441]

22 11.5 KLRF1 Killer cell lectin-like receptor subfamily

F, member 1 [ENSSSCT00000000711]

11 20.4 C4pre Complement C4 precursor [C4β chain;

C4α chain; C4a anaphylatoxin; C4γ

chain] [TC478078]

23 10.4 HAMP Hepcidin antimicrobial peptide

[NM_214117]

12 17.6 NLRP5 NLR family, pyrin domain containing

5 [NM_001163407]

24 10.3 PBD-2 Beta-defensin 2 [NM_214442]

208

Appendix II: continued.

Rank GER Gene


Gene



[BX918848]



26 9.1 CLEC5A C-type lectin domain family 5, member A

[NM_213990]

43 5.5 KLRC1 Killer cell lectin-like receptor subfamily

C, member 1 [AJ942142]

27 8.9 LBP Lipopolysaccharide binding protein

[NM_001128435]

44 5.5 DHX58 DEXH (Asp-Glu-X-His) box polypeptide

58\RIG-I-like receptor LGP2

[NM_001199132]

28 8.9 BD4 Pre-pro-beta-defensin 4 [NM_214443] 45 5.5 TLR6 Toll-like receptor 6 [NM_213760]

29 8.2 BD114 Beta-defensin 114 [NM_001129973] 46 5.4 BD125 Beta-defensin 125 [NM_001129974]

30 8.1 LGALS13 Galectin 13 [NM_001142841] 47 5.4 BD3 Pre-pro-beta-defensin 3 [NM_214444]

31 7.9 SELPLG Selectin P ligand [NM_001105307] 48 5.2 SELL Selectin L [NM_001112678]

32 7.9 SFTPA1 Surfactant protein A1 [NM_214265] 49 5.2 MYD88 Myeloid differentiation primary response

gene 88 [NM_001099923]

33 7.4 C1qTNF9A Complement C1q tumor necrosis factor-

related protein 9A-like

50 5.1 LEAP2 Liver expressed antimicrobial peptide 2

[NM_213788]


[NM_213738]

51 5.1 C7 Complement component 7 [NM_214282]

35 6.9 DDX58 DEAD (Asp-Glu-Ala-Asp) box

polypeptide 58/ Retinoic acid-inducible

gene 1 [NM_213804]


36 6.8 CLEC1B C-type lectin domain family 1, member B

[ENSSSCT00000000704]

53 5.0 KLRB1 Killer cell lectin-like receptor subfamily

B, member 1 [TC451162]

37 6.6 DDX60 DEAD (Asp-Glu-Ala-Asp) box

polypeptide 60 [XM_001927633]

54 4.7 FCN2 Ficolin-β (hucolin) [NM_213868]


A [TC453642]

55 4.6 KLRK1 Killer cell lectin-like receptor subfamily

K, member 1 [NM_213813]


[ENSSSCT00000000700]


40 5.7 TLR4 Toll-like receptor 4 [NM_001113039] 57 4.4 C8A Complement component C8A

[TC447323]

209


Rank GER Gene


Gene



59 4.3 C1S Complement component 1, s

subcomponent [NM_001005349]

74 3.7 CD55 CD55 molecule, decay accelerating factor

for complement [NM_213815]

60 4.2 C5AR1 Complement component 5a receptor 1

[AK344310]


61 4.2 NLRP3 NLR family, CARD domain containing 3

[ENSSSCT00000008719]


A [TC471307]

62 4.2 IFIH1 Interferon induced with helicase C

domain 1 (IFIH1)/MDA5

[NM_001100194]


[NM_001184947]

63 4.2 CFH Complement regulator factor H precursor

[TC475926]

78 3.6 BD121 Defensin, beta 121

[ENSSSCT00000007900]

64 4.1 CD14 CD14 molecule [NM_001097445] 79 3.5 CLEC4G C-type lectin domain family 4, member

G/ liver and lymph node sinusoidal

endothelial cell C-type lectin

[NM_001144117]

65 4.1 FCN1 Ficolin-α [NM_214160] 80 3.5 TLR10 Toll-like receptor 10 [NM_001030534]


protein [NM_214170]

81 3.5 C1QC Complement component 1, q

subcomponent, C

chain[ENSSSCT00000003916]

67 4.1 LGALS9 Galectin 9 [NM_213932] 82 3.5 TREM2 Triggering receptor expressed on myeloid

cells 2 [ENSSSCT00000001794]




[NM_001097448]

69 4.0 SELP Selectin P [NM_214078] 84 3.4 CD302 Type I trans membrane C-type lectin

receptor DCL-1 [TC465837]

70 4.0 CFD Complement factor D (adipsin)

[ENSSSCT00000014662]


[NM_001163648]

71 3.8 TLR7 Toll-like receptor 7 [NM_001097434] 86 3.4 BD122 Beta-defensin 122 [TC499283]


[ENSSSCT00000000703]


[NM_001097449]

210


Rank GER Gene


Gene



[NM_001001646]

102 3.1 C4BPA Complement component 4 binding

protein, alpha [NM_213942]

89 3.3 MBL1 Mannan-binding lectin A

[NM_001007194]

103 3.1 BD103A Beta-defensin 103A precursor

[TC424333]

90 3.3 BD123b Beta-defensin 123 isoform b -

HTC438801]

104 3.1 C3 Complement component 3 [NM_214009]

91 3.3 LGALS1 Galectin 1 [NM_001001867] 105 3.1 C2 Complement component 2

[NM_001101815]

92 3.3 C1QA Complement component 1, q

subcomponent, A chain NM_001003924]

106 3.1 KLRG1 Killer cell lectin-like receptor subfamily

G, member 1 [ENSSSCT00000000719]

93 3.3 C1QB Complement C1qB Fragment

[ENSSSCT00000003919]


94 3.2 C1esterase Complement C1s subcomponent

precursor (C1 esterase) [TC413063] N/A 3.0 ACTB Beta-actin [AK237086]

95 3.2 LGALS8 Galectin 8 [NM_001142827] 108 3.0 DEFB1 Defensin, beta 1 [NM_213838]


[NM_001123089] N/A 3.0 HMBS Hydroxymethylbilane synthase

[ENSSSCT00000016474];

[NM_001097412]


protein [NM_213888]

109 3.0 C8B Complement component C8B

[NM_001097451]

98 3.2 BD109 Beta-defensin 109 [TC453775] N/A 2.9 SDHA Succinate dehydrogenase complex,

subunit A [AK350046]

99 3.2 BD129 Beta-defensin 129 [NM_001129975] 110 2.8 NLRC5 NLR family, CARD domain containing 5

[EU350951]

100 3.1 CFP Complement factor properdin

[ENSSSCT00000013427] N/A 2.7 B2M Beta-2-microglobulin [AK346048];

[XM_003121539];

[ENSSSCT00000005170];

[NM_213978];

[ENSSSCT00000005176]


211


Rank GER Gene


Gene


112 2.5 C8G Complement component C8G

[AK233484]

113 1.7 C1r Complement component 1, r

subcomponent [ENSSSCT00000000733]

N/A 2.4 HPRT1 Hypoxanthine

phosphoribosyltransferase 1

[ENSSSCT00000013865];

[NM_001032376]

114 1.6 CFB Complement factor B [NM_001101824]

N/A 1.8 GAPDH Glyceraldehyde-3-phosphate

dehydrogenase [AK234838]

212

APPENDIX III: COMPARISON OF RANKING OF ALL INNATE IMMUNE RESPONSE GENE PROBES

Genes are ranked based on the calculated gene expression ratio (GER). The GER for each gene was calculated by comparing the mean gene expression ratios

(Log2) after excluding high and low expressing outliers (n = 2) as follows: top 50% (n = 43) of pigs to the bottom 6 % (n = 5) of pigs; top 50 % (n = 43) of

pigs to the bottom 10 % (n = 9) of pigs, top 10 % (n = 9) of pigs to the bottom 10 % (n = 9) of pigs, top 20 % (n = 17) of pigs to the bottom 20 % (n = 17) of

pigs, top 50 % (n = 43) of pigs to the bottom 50 % (n = 43) of pigs as well as the top 6 % (n = 5) of pigs to the bottom 50 % (n = 43) of pigs. Text in

parenthesis indicates Ensembl or GenBank reference sequence.

Gene Symbol Gene Description

Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

DDX3Y ATP-dependent DEAD (Asp-Glu-Ala-Asp) box

polypeptide 3, Y-linked gene [AK344932]

1 1 1 1 1 4 2

MBL2 Mannan-binding lectin C [NM_214125] 2 2 2 3 2 1 2

PR39 Peptide antibiotic PR39 [NM_214450] 4 4 4 4 4 3 4

SCGB1A1 Secretoglobin, family 1A, member 1 (uteroglobin)

[ENSSSCT00000014276]

3 3 3 2 5 7 4

PMAP-23 Porcine myeloid antibacterial protein PMAP-23

[NM_001129976]

5 5 5 6 3 5 5


[ENSSSCT00000012426]

6 6 6 5 6 8 6

SFTPD Surfactant protein D [NM_214110] 8 8 7 7 7 2 7

NPG4 Protegrin 4 [NM_213863] 7 7 8 8 8 6 7

ITLN2 Intelectin 2 [NM_001128453] 14 11 9 9 9 9 10

213

Appendix III: continued.


Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

PGLYRP1 Peptidoglycan recognition protein 1

[NM_001001260]

9 9 10 11 13 18 12

pPGRP-S Peptidoglycan recognition protein S [AK231441] 13 15 11 14 11 10 12

SELE Selectin E [NM_214268] 20 13 12 10 10 14 13

HAMP Hepcidin antimicrobial peptide [NM_214117] 10 10 13 15 18 23 15


[NM_001129965]

19 17 14 12 12 20 16

LBP Lipopolysaccharide binding protein

[NM_001128435]

11 12 15 17 19 27 17

PBD-2 Beta-defensin 2 [NM_214442] 18 14 17 16 15 24 17

KLRF1 Killer cell lectin-like receptor subfamily F, member 1

[ENSSSCT00000000711]

21 18 16 13 22 22 19

LGALS12 Galectin 12 [NM_001142844] 24 22 18 18 16 19 20


BD108-like Pre-pro-beta-defensin 108-like (LOC692190),

mRNA [NM_001040641]

29 30 24 21 20 15 23

DDX58 DEAD (Asp-Glu-Ala-Asp) box polypeptide 58/

Retinoic acid-inducible gene 1 [NM_213804]

16 19 23 25 29 35 25

214



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

BD104-like Pre-pro-beta-defensin 104-like [BX918848] 23 25 20 27 30 25 25

C4pre Complement C4 precursor [C4β chain; C4α chain;

C4a anaphylatoxin; C4γ chain] [TC478078]

48 37 21 20 14 11 25

PGLYRP2 Peptidoglycan recognition protein 2 [NM_213738] 17 21 22 26 32 34 25

CLEC1B C-type lectin domain family 1, member B

[ENSSSCT00000000704]

15 20 25 30 26 36 25

SFTPA1 Surfactant protein A1 [NM_214265] 26 23 27 22 28 32 26

MYD88 Myeloid differentiation primary response gene 88

[NM_001099923]

12 16 26 24 33 49 27

ZBP1 Z-DNA binding protein 1 [NM_001123216] 49 41 29 23 17 17 29

KLRC1 Killer cell lectin-like receptor subfamily C, member 1

[AJ942142]

25 24 32 32 31 43 31

SELPLG Selectin P ligand [NM_001105307] 37 31 31 31 27 31 31

NLRP7 NACHT, leucine-rich repeat and PYD containing 7

Fragment [ENSSSCT00000003642]

59 48 30 28 23 13 34

LY49 Killer cell lectin-like receptor subfamily A, member

1 [NM_214338]

53 47 33 33 25 16 35

215



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

CLEC7A C-type lectin domain family 7, member A

[ENSSSCT00000000700]

30 29 37 38 35 39 35

NLRP5 NLR family, pyrin domain containing 5

[NM_001163407]

66 51 28 29 24 12 35

FCN2 Ficolin-β (hucolin) [NM_213868] 22 27 35 37 41 54 36


NOD1 Nucleotide-binding oligomerization domain

containing 1 [NM_001114277]

35 34 40 36 37 42 37

BD3 Pre-pro-beta-defensin 3 [NM_214444] 39 32 42 34 34 47 38

SELL Selectin L [NM_001112678] 27 28 36 39 50 48 38

TREM1 Triggering receptor expressed on myeloid cells 1

[NM_213756]

32 35 38 40 44 41 38

TLR4 Toll-like receptor 4 [NM_001113039] 36 36 41 42 40 40 39

DDX60 DEAD (Asp-Glu-Ala-Asp) box polypeptide 60

[XM_001927633]

40 43 39 44 49 37 42

KLRB1 Killer cell lectin-like receptor subfamily B, member 1

[TC451162]

38 38 45 43 38 53 43

C7 Complement component 7 [NM_214282] 31 39 43 45 47 51 43

216



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

C1S Complement component 1, s subcomponent

[NM_001005349]

33 33 44 41 46 59 43

NOD2 Nucleotide-binding oligomerization domain

containing 2 [NM_001105295]

41 44 54 50 48 68 51

C1qTNF9A Complement C1q tumor necrosis factor-related

protein 9A-like

76 63 47 47 43 33 52

LEAP2 Liver expressed antimicrobial peptide 2

[NM_213788]

57 54 49 48 51 50 52

CD14 CD14 molecule [NM_001097445] 43 45 51 53 53 64 52

NLRP3 NLR family, CARD domain containing 3

[ENSSSCT00000008719]

52 49 58 49 45 61 52




C5AR1 Complement component 5a receptor 1 [AK344310] 54 58 64 58 55 60 58

CD302 Type I trans membrane C-type lectin receptor DCL-1

[TC465837]

34 42 48 67 76 84 59

217



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank


[NM_213990]

104 95 46 46 42 26 60


[ENSSSCT00000000703]

44 53 61 70 63 72 61

C8A Complement component C8A [TC447323] 69 60 62 57 59 57 61


CLEC4G C-type lectin domain family 4, member G/ liver and

lymph node sinusoidal endothelial cell C-type lectin

[NM_001144117]

47 46 56 68 72 79 61

BD125 Beta-defensin 125 [NM_001129974] 93 80 65 51 39 46 62

CD59 CD59 molecule, complement regulatory protein

[NM_214170]

61 64 66 61 65 66 64

IFIH1 Interferon induced with helicase C domain 1

(IFIH1)/MDA5 [NM_001100194]

64 66 70 65 61 62 65

FCN1 Ficolin-α [NM_214160] 71 61 68 64 60 65 65

KLRK1 Killer cell lectin-like receptor subfamily K, member

1 [NM_213813]

79 67 60 66 68 55 66


218



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank


DHX58 DEXH (Asp-Glu-X-His) box polypeptide 58\RIG-I-

like receptor LGP2 [NM_001199132]

84 83 63 69 57 44 67




MASP1 Mannan-binding lectin serine peptidase 1

[NM_001184947]

60 62 75 71 71 77 69

SELP Selectin P [NM_214078] 85 68 72 60 64 69 70


BD4 Pre-pro-beta-defensin 4 [NM_214443] 110 110 55 62 62 28 71

MASP2 Mannan-binding lectin serine peptidase 2

[NM_001163648]

65 65 76 73 77 85 74

CFH Complement regulator factor H precursor

[TC475926]

91 84 77 75 80 63 78

BD123b Beta-defensin 123 isoform b - HTC438801] 62 71 80 84 83 90 78

219



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank



CD55 CD55 molecule, decay accelerating factor for

complement [NM_213815]

75 87 84 82 78 74 80


[TC471307]

88 81 78 78 82 76 81

C1esterase Complement C1s subcomponent precursor (C1

esterase) [TC413063]

80 70 81 79 86 94 82


BD103A Beta-defensin 103A precursor [TC424333] 70 79 91 85 79 103 85

C4BPA Complement component 4 binding protein, alpha

[NM_213942]

63 77 89 87 93 102 85


CD46 CD46 molecule, complement regulatory protein

[NM_213888]

73 82 86 83 96 97 86


TREM2 Triggering receptor expressed on myeloid cells 2

[ENSSSCT00000001794]

90 86 87 89 90 82 87

220



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank

CFD Complement factor D (adipsin)

[ENSSSCT00000014662]

98 96 83 90 91 70 88


[TC453642]

111 111 90 95 98 38 91


MBL1 Mannan-binding lectin A [NM_001007194] 87 91 93 96 94 89 92




BD109 Beta-defensin 109 [TC453775] 99 97 101 99 88 98 97

KLRG1 Killer cell lectin-like receptor subfamily G, member

1 [ENSSSCT00000000719]

94 92 98 97 97 106 97

DEFB1 Defensin, beta 1 [NM_213838] 96 99 106 100 85 108 99

C1QC Complement component 1, q subcomponent, C chain

[ENSSSCT00000003916]

103 104 100 105 105 81 100



221



Rank

Top 50%

to

Bottom

6%

Rank

Top 50%

to

Bottom

10%

Rank

Top 10%

to

Bottom

10%

Rank

Top 20%

to

Bottom

20%

Rank

Top 50%

to

Bottom

50%

Rank

Top 6%

to

Bottom

50%

Average

Rank


C1QA Complement component 1, q subcomponent, A chain

NM_001003924]

100 105 102 104 106 92 102

BD122 Beta-defensin 122 [TC499283] 108 109 105 103 103 86 102

C1QB Complement C1qB Fragment

[ENSSSCT00000003919]

102 106 103 110 110 93 104

CFP Complement factor properdin

[ENSSSCT00000013427]

107 107 108 101 101 100 104

C8B Complement component C8B [NM_001097451] 101 102 107 109 109 109 106

BD121 Defensin, beta 121 [ENSSSCT00000007900] 112 112 112 112 112 78 106

NLRC5 NLR family, CARD domain containing

5[EU350951]

106 103 110 107 107 110 107

C8G Complement component C8G [AK233484] 105 100 111 111 111 112 108

C1r Complement component 1, r subcomponent

[ENSSSCT00000000733]

113 113 113 113 113 113 113

CFB Complement factor B [NM_001101824] 114 114 114 114 114 114 114

222

APPENDIX IV. TARGET INNATE IMMUNE RESPONSE GENE SEQUENCES WITH ANNOTATED SNPS

Figure IV.1. Sus scrofa SCGB1A1 amplified promoter sequence.

Genotyped SNPs are indicated in bolded, underlined and highlighted. Deletions and insertions are indicated as bolded with strikethrough or between brackets

respectively. Bolded sequence represents coding region of the SCGB1A1 gene with the ATG start codon underlined.

-1903 TTTTTTTTTTTTTTTTGTCTTTTTGTCTTTTTAGGGCCGYACCCGAGGCATATGGAGGCTYCCAGGCTAGGGGGTCTAAYCAGAGCTACAGCTGCTGGC

-1804 CTACACCATGGCYACAGCAACGCCAGATCCGTAACCCACTGATSGAGGCCAGGGATYGAACCCACAACCTCGTGKTTCCTAGTCAGATTYGTTTCCRCT

-1705 GCRCCACAAYGGGAACTCCTAGCAAGTTCTTCTTAAAGGGGYCCCAAGGCAGGGCTGCTCCATATCTCAGCCAACTCCCAGCTCCTAGCATGGTGCCTG

-1606 GCACATAGCAGGTGCCCAGCCCTTGAATGAATGAATGAACATTATTGAATCTCGAAATACAGATAGGATTCAGAGAAGGAGACAAGGCAGATGCRTGTT

-1507 CCAGGCACCAGGCCCAGCTCGTGCAAAGGTAAAAAGACAAGGAGCATCCCCAAATCAGCAAATACTAAGAAGGGGTTAAATCCCCTGTAGGGGAGCAGA

-1408 GGAGTGAGGCTCGAATGGTAAGCAAAGGCCAGTGGACAGGGCCTTGTAAATCACACTTGAATTTTATCCCTTCCGCCAAAGGAAGTCTTCCAAGGGTTT

-1309 CAGGAAGGAGGAGGATGAAATCCGTGGGTTTTAGAAAGATCATTCTGGTGGCCTTTCCGAGGATGGCCCAGGAGGACGAGCCAGGAGGCAGGAGCCCAT

-1210 CTAGGAGGTGACTTTGACCCTGCCAGGCCTGTGTTCTAGGGCACAGGCATCGGARAAGAAAGGARGCAGCCACTGACATGGTGGCAGGAGACAGGAAGG

-1111 GGCCACGGCSCCAGCCTGGAACCCCCAACGCATCAGCTCAGTCARTAAAGAATCAAAGTCT<GGAGTTCCCGTCGTGGCGCAGTGGTTAACGAATCCGA

CTAGGAACCATGAGGTTGCGGGTTCGATCCCTGCCCTTGCTCAGTGGGTTAACGATCCGGCGTTGCCGTGAGCTGTGGTGTAGGTTGCAGACGCGGCTC

GGATCCTGCGTTGCTGTGGCTCTGGCATAGGCCGGTGGCTACAGCTCCGATTCAACCCCTAGCCTGGGAACCTCCATATGCCGCGGAAGCGGCCCAAGA

AATAGCAACCATAACAACAACAACAACAACAAAAAAAAAAAAGACAAAAGACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGA

-1050 ATCAAAGTCT>ACAGAACAGGGACGGCTGAAGGGAAAACAGGAAAGAACAGGAGTTCTCGTVGTGGCTAGGAACCATGAGGTTGCGGSTTCGATCCCTG

-962 GTCTCGCTCAGTGGGTTAAGGATCTGGCGTTGCCGTG<GTG>AGCTGTGATGTARGTCGYAGACGCGGCTCAGATCCTGAGTTACTGTGGCTGTGATGT

-868 AGGCCRGCGGCTACAGCTCCAATTCGACCCCTAGCCTGGGAACCTCCATATGGCACAGGTGTGGCCCTAGARAAGACAAAAAAAAACAAAAAACAAAAA

-769 AAAACAAGAAAGAACAGAGCCRTGGGAGCACAGGAGAGAGAATGCAGGAAATGACAGGGGGTCAAAGCCATTAAAAGGTCAAGAGGGATAAGGCCTGAA

-670 GTGCCCGCGGACTTGCCCTCAGGGGGCAGGACTCCAGAGCCAGCTGGCGCAGGGCATCCTCCAGCTTGACCCAGGGCTTGGGTTTCTCAGGGTGTTCTT

-571 TATCCCYCAGCATGCTTCTGTCCAGGCTCTCCCCCCAAGTCAGACCACAAGAGGGTCTGGCYCATATGATCCTCAAGGCTTGAGGACCAGCCGCTTCCT

-472 GGGAGAGGAGCCCAGCGGGGTACCAGGAGTGCCAAGTCCTAGTCCTGTCCCTGCYGCTTGGGCCTTGGGCCTGAGCTTCCAGAGTGTTGGGTCCAGATA

-373 GGATTGACAGWTGCTTCYGTCTGTCGATCTGGACTGCCCAGGGCTCAAGGTCAAAGGTGGGTGGCCCAGGCCACCAGGTCTCCAAACCCTGACTGGGGA

-274 ACCTAGCTGCCTCCCCACAGGACTCTGGGTTACCCCCTTCCAAGTAGCCAATAGGCGAGCTCAGTTTCAATGGACACAGAATGCAGGTTGGGAAAGGAG

-175 AATATTTACTTTTYCCACGGAGCTGATGCCCAAATAAATAGTGTGGTCCCCGAAGTGGAGCCCACGCCCTGCCCTCCCCTGTCCAGGAGCCTATAAGAA

-76 AGCRGACCRGCACTTCTCCCGCAAGACCACCGGACCAGAGACAGGACTGGGGCCTCCCACCAGCCTCYGCTCCACCATGAAGCTGGCCGTCACCTTCAC

+24 CTTGGTTGCCCTGATCTTCTTCTGCAGCCCTGGTGAGTGCCCAGAGCCCCTGTGCCCCAAGCCYGGCTTGGGAACTCTCCCAGCTCCCCGTCCCGCTCG

+123 GGAGATGGGGGCAGCTGTCAGGTCCTCTGCTGAGCTGCGTCCCGTCTTGGGAATGTGGGGAGAGCCCTAGGGCTGCGAGGTGGCCTGAAAAGGACCCCA

+222 TCTTCCGTWCCCAGCAACCTCAGCGCTTCAGGGGATGGACAGACYGCAGGGAGGGATGGGGAAACGCC

223

Figure IV.2. Sus scrofa SFTPD amplified promoter sequence.

Genotyped SNPs are indicated in bolded, underlined and highlighted. Bolded sequence represents coding region of exon 0 of the SFTPD gene (Note:

proposed ATG start codon is only present in the next exon and is not shown).

-5328 CCATCAGACAAACCACAAGCACAAGGCTGCTACTTTTAAGCTGGAAAGAGACTCTGTGGCTAACAATGTCAATATAATGGAAGAGAAAGACATCTCTCA

-5229 TGGTGGTCAGATGCCACAGGACCCCACATGGCAGTGGACGACCACTTCAGGATTACCCCCCTAACTTTCCATACCTTTTCCTTATTTCTTGACATCTCG

-5130 GCACTCACAGGAGTTTCCTTGGCCTCTTGGCTGGCTCCTCAATTGTTGGGCTGCCCACCCACTGCAGGCCTGCAAGCCTTGTAGTTGCCCAACCTTGAG

-5031 ATGGAAGAAAGAGCCCAGACACACTGACAGAGCCATCAGTGGCTTATTGGACAGGGGATCTTACATCTCCAAAGCAGAAGGGTCCTAGAGCAACACCCC

-4932 CACTGTGTATGGCAGGACAGTCAGCAAACTTCATTGCTGGTGGGAGGAGGCTATCATTTATGGGGGAACTGACGTCAAGTTGGCTCACCAGTTGCCAAG

-4833 GAAACCAGCAGCTGGAGCAGGGGAAAGCATGTGGGTACTTACCAATTAAGATCTATAATTAAAAGGATTGGATAGTCACATGAGTGAAGTAGGGTCTGG

-4734 CCGAGCTGGTGATGTACAGAGAGCAAGAGAACAGCCGTCTTGGATGACCTGACTATACCTATGTCCACTGAGCTGGGAGTTTCCACAGTAATGTGGGCA

-4635 ATCAGCTGGTAAAATACCAGAGGCTACAGCTTAGCTCTGACAAAGGTGCAGCTAATGAAATCCACCAGGGGTTTCTGATATTGCTGGGCTGCAGTGCAG

-4536 CAGTGGTGACTAGCTCCCAAAGAAAGCRTGTAGTTATCCTGACCTCATCTTGGGAAGAGAGGGTGAGCCAGTGATCCTCTGCATGAAAGCCATTGTGAT

-4437 CACCATTTAAAATCTGATTCTCAGAGTTCCCTGGTGGCCTTGCRGTTAAAGATTTGGCATTGTGACCACTGTGGCTCAGGTTCAGTGYCTGGCCCAGGA

-4336 AATTTCACAAGCTGTGGGTGCAGCCCAAAATATAAAATCAGATCAAATCTGATTCTTCTCACTTGTGTAACTGAGAAAAGCAAAGGTTTTCACTGGAAC

-4237 ATGAGTGTCTGGGTTGGATCATAAGTAGACCTGGACCTTGGTGGAATGTGGAGTTAGATAAAGAAACTCCATATTCTTTGCTATAATGGGGTCCAAGGG

-4138 CATTGTGAGGGATGAATCTGACACCCTAGGAGTTAGCAGTTAACAGAAGTCAGCTTGCAGGAAGAAACAAAGTATAGGACTCCTTTAATAAGGGTCATC

-4039 CTAAATAAGAATTTTGTCTAGCCACCAGGATAAGACTTGACAATTAGGATTTGTGGGGAGAGGAGAACAAGGGTTCAGTTCAGCCTCCATGCTGACTTA

-3940 GATCTCCAGGGGCACAAGAACATCCTAGAATAGAGGGGGCTGTGTTAGTGATGAAAGGGCTCAAACATTAGGGGCCCAGGTGCTCTGCTATGGGATCCT

-3841 GCTTCAAAAAATTGCAACATGGGAAACAGAAGACCTTTTCTTATCAACTGAGGAAAACTGGCTTTATAGGTTCCACAGTATACAAGGTGATGGCATCAA

-3742 AAGCTAGGAGCAAGTCAGCACCTCCAAGGGGGTGCCCATAGGAAAGGACTGGAAACATGCGGCTGCTGGTGTATAGACCTAGGCAAAGGGTGGATGGAA

-3643 GAGATAAAGTCACAAGGATCTAAAAGCAAGCAGAGCTGACAGCCACAGCAGTAGGGTGGGGAAATGCCCTACAGTCACTAGAAGTTAGAGTTACCCTGG

-3544 GGATGGTTACGACAGTGTATCAGCAGCTCAGGGGTCCAAACTGGCCACTAGAGCAATGTAATGGGCAAACACAAGCTAAAGAGATGGAGAGATTTGGGC

-3445 AAGGAAGGCCATCCCACAAAAGGCAAGTGGCAGGGGGCACTCTTAGATCCAGAGCAGAGAGCAAAAGAGTGACCCCTGCTAGGTGGTAGCTCCTCCAAC

-3346 CGCTGCCCCCACCCCAGGCTGCTACCTAGCACTTCCTCTACAAGGCTACTCCCACTCAGGTATACAAGGAGCTCCCAGCTCTTTCCTAATATCTAGGCA

-3247 GTAATGTTGAGGTGAAGGGGGAAGAGAAGTGGGCACAGTAGGTGCTGGCTCTTGGATTCTGCAGATGCAGGTTGCTTTTGCAATAGTTGTAGGTCACTG

-3148 TGCAACTGGCTGGTCTTCTCTGGACCTTGAATTCCTGGACATCTGTAAAATACAGACACTGTTGCTGCCACTTAACTCCAAGGGTTGCAATGAGATGCA

-3049 GATGAGAGCGTGGACTGAGGTGCTCTATAAACTCTAAGGTGATGGGTGTGTAGTGTTATGAACATCAGTGGCAGGTGTCCAGAATGCAGGTGATCGAGT

-2950 GAGTCAACAAGGAAGAAAATTGCTCTATCTACTTCTTGAAGAGGGTTCTCAGGAAACTGGGGCTGGGAGGCCCAGGTTACAGGGCAGTCATAAATAGCC

-2851 AGTGCCTGCCCAGAAAACTTTAGTTTGCCTGGAGATTCTGGAGCTCTAGAGGACGCAACTGTGAGTGTTTCTGGTCTTGCATCTCCTTTTGTTCTCCTG

-2752 ATGTCCAGTGAGTAGCTCCCTGCCTCTATGGGTGGCTTATCCTACCAGTGTTGAGGAAGGCAGGGTCTGTGGAGCTGTTCAGGCCTAGGAGGGTGGGTG

-2653 TTGGAGGTG

224

Figure IV.3. Sus scrofa HAMP amplified promoter sequence.

Genotyped SNPs are indicated in bolded, underlined and highlighted. Deletions are indicated as bolded and strikethrough. Bolded sequence represents coding

region of the HAMP gene with the ATG start codon underlined.

-2446 TATCCCACTGCCTCCTTGGTCTCTAGAGGTACTGACACAGGGTGCTTACGGGAAGGGGGGGAGCCTTTGGGGGCCAGCCCCGGGGCCTGGGCCTAAGCA

-2347 GGGAGGCCATGTCCCACCCCACCTCTTGTTTCTGGAACCCTGCTCCCCTTTGGGTGTGTGAGTGTGTTTTAATTTTCTTTATGGAAAAATGGACAAAAA

-2248 AAAGAGAGAGAGAGAGAGAGAGGTATTTAACTGCAATAAACTGGCCCCATGTGGCCCCGCCTTGTCTGTTTGTGTATCTGTCCATCTCAGGTGTCGGGA

-2149 GGGGGCCYGGGGTCTATGCAGAGCTCCTGAGGCCAGGACCTCAGCTGTCGTGTGTGTGGCCGTGTGCCAGTCCTTGGCGTCCTGTACCACCTGGTACCC

-2050 AGTTTGTTGGTCATAGGGATGGAGGAATTCAGGAAGGAATAGCTTCTTTGAGGCCCCAGGTGTGTATATGTGGTGTGGGGGCAGGAAGAGCCGGGGTCA

-1951 AGGACATGTCCCATGTGTTTGGAGAAGAGGCTGGGGTCTCCTGTGTTACCAGTTCCTAAAAACAGGACTCACTCCTGGCCCTGCCCTTCTGGGCTGACG

-1852 CCCTCCCCTCTGGACCAGCCAATGGTGGGGCCTGGCCTTGAGCCCCCCACCCCCAGGGAGGGCAGATGGCCAAAAAGCCAAGCTTGGCCCGTCAGCCTG

-1753 TCGCCTTGCACCGCGACTCTGGCGCCTGTGCTGTGTGACCCCTGCCCCTGGCTGATGATGAAACCTGGCCTGAGCTGAGATGCAGTGATGCCCAGCAGG

-1654 GCTGGGGGATGCTGCTATGTCTCCCTGTGGATGCRAGGGCGGCCTTCCCCCAGACCCTGCCTCAACCAGCAGCCCCTGCGCAGCTCCAGCCACTCCTAG

-1555 AATCTAGGCCTGCTGSTCTGGTCACCTTGCTGAGCTCACCACCCTGCGCCCACCCCAAGTGCCCCCAGCTGGTCTCCTCCCTGTGCGAACCCTGTCTGC

-1456 TTTTCCTGGCCATTGCTCTCTCTGAGGCCGTCTTCSGGAGGGAGGGTCATGSAGCAGGAGGAACCGAGCCTAGAGTGCTTGGGGAGGCGGAGGTGGGGA

-1357 ACAGCGCTACATCCCAGGGGCCTCCTGTTTTTGTGAATCTTTTTTTCCAGGGGGCCTTGACAGCATTTGAGGGCCAGGAGGTATTCATCCTTGGCCACC

-1258 GTGACAGGCTGATGCTGGGTGGCCCAGAGTGAGTTGGAGGAGGAAATGCCCAAGGGCCCGTCTCTGGAGTCACTGTTTGCCATTCCCCTGAGCCATAGG

-1159 CATCCTGAGATGGTTCCAGTGGCGGACAGGCATGAGRTGGCCACAGCCAGGCGGCCTGAGCTCTGCTCCCTTTCTGGCCATGCTCGGGCAGCAGGCTCC

-1060 TGGAAGAAAAGCCCAGCTTGGGGTGTGTGCTGTCGTCTGTGRCCCGAGYGCCCCACCACTGCTGGTTTCCAGGTGCCAGTGCCCGGCCCTGACTGCGGA

-961 GTTGGGATGAGCCAYGCACGATCTGCTTGCCAAGCCATTATGCCCCAGGCCCAGCAGCCSCCAGCCCCAACCCCRTGCCTTCCTGGGTCTCCAGAGAGG

-862 CAGGAAAGCCTGGGGAGAAGGCCACAGCCCCAGTCAGGCTGCCTGGGCCGGAATCCCGGCTCTGCCTCCGGCTGGGCGAGCTTGGGCCGTGCCCTGGGC

-763 TTGGCCTTTAGTTCCTCCCTGTAAAGTGAGGAAAATGAGGCTCAGGTGAGCACGATGGGTTCCTCTCTCGGGAGCAGCGTCTGGGAGGCCAGGCCCCTG

-664 GGGTCAGTGGCTGGGACAGCAGCGAGGGCCCAGAACAGGGAGCAGAGCCCAGGATGGGGCAGGCGGGAGCCGCTCCGAGGCCAGGTCGCCAGGGCTGAG

-565 TTAACACAAATGTGAGTCCCTATCTCTGCTGGCTTGTGTGGTGCGGTCCTCAGATGTGAGTTGGCTGTGACTGTCACCACTGTCTTTGGGGGCCGAAAA

-466 TTCACGGGGACATTTCCCAGATACCAGGGCCGCATCTTAAGGTTCTGACGCTTTTGGAAAAGCCCACACACGCACCGGTGGCTCCTGCGGACACAAACT

-367 TCCGCGCCTGCCCATGTCCCCTCCCAGAAGCGAACCCCTGAGGGTTCCGCCAAGGGACAGTCAGCCTCCTTGTGAATGAGCAGGTCCGGGAAGGGCRGG

-268 GAGGAGGGCACCTTGCTCCTGCTCATCGACCTGTTCAACCTCCTGGGCGAAAGGGTTTTGGTTTTTGTTTTTGTTTTTTAAATCAACAGGGTGATGTCC

-169 CGTCRGGGACAGTGTCTCCCAGGTGGCTGACTCCAGGCGGGTGTCTGTGGCCGCATCGGCCCCACCTCCTGGACACACCTCTGCTGGCCAAGGGTGACA

-70 TAACCCTGTTCCCTGTCACTCTGTTCCCGCTTATCTCTCCCGCCTTTTGGGCGCCACCACCTTCTTGGAAATGAGTTGGGCCAAAGGG

225

Figure IV.4. Sus scrofa DDX58 amplified promoter sequence.

Genotyped SNPs are indicated in bolded, underlined and highlighted. Deletions and insertions are indicated as bolded with strikethrough or between brackets

respectively. Bolded sequence represents coding region of the DDX58 gene with the ATG start codon underlined.

-2369 CAGCAGAAGGAGCAGATGGTGGTGTCCCAAAGAACCATCTTGCCTGAGTCAGAATTCAGGCTTCTTTTATACTAAATGGAGAAGAGATGTAGCTGGTTG

-2270 TTGCAAACTTCTTGGGGCGGGAATCCTTTGTTCTTGCAGCTRTCCATGTAGGTCTGGTCAGAGTGTTATTATAAACCTCCAAGGCAAATATTGTTATAT

-2171 TCTCTGCAGCAACTTTTTATCTCTATATGAGTGGAAGTTTTTTACCTTGGAAGGTCAGAACCTTGAGAATGAGCTATCCCGTRTATTTCAGGCTCGAGG

-2072 CAACATTCTTTTGAGTATGAGGAGCTCTTGGTGCAGAGCCAGCATGGCTGAGCACAAGCAACAGAGCACACGTTTAGARCTAAAGGAGTATATTCAATA

-1973 TGGAATCAGGTTTATTCTTCTCTGTTACAAATTTTGTAATTAAAGAATGTTTCCCTGCTGAGATTAGTAATAAGGTAAGGGTATCAACTCATCACTTTT

-1874 ATTCAACTTTCTATTGGAGACCATAGGTGTTGCCTTAAGGAAGGGAAACAAAA<TAAAA>GGCATGAAGATTTGAAAGAATAAAACCAGGTATTCACAA

-1782 GTGACATGATTGTTTACCTAGAAAAATTTAAGAGATATACAGAACAATTACTAGAGCTAAGTAAATCAATGAATTGCATAATCCAAGTGAATTGTGTAA

-1683 TACAAGGCCAAGAAACAAAAACCCCTTTTATTTCTATGTACTAGCAACAAACACTTTGAAAATGAAACTTTAAAAACAATTTAATTTAGGGAGTTCCTT

-1584 TCATGGCTCAGTCGTTAAGGAACCTACTAAGAACCATGAGAATTTGGGTTCCATCCCTGGCCTCGCTCAGTGGGTTAAGGATCCAGCATTGCAGTGAGC

-1485 CGTGGTGTGAGGAGATGTGGCTGGGATCTCATGTTGCTGTGGCTGTGGTGTGGGCCTGGCAGCTGTAGCTCTGATTAGACCCCTAGTCTGGAAATTTCC

-1386 ACATGCTGTGGGTGTGGCCCTAAAAAAAAAAAAACCAAAAAACCCCTCAAACAATTCAATTYACATTAGCATCAAAGMACATAAAATAGTTAAGAATAA

-1287 ATTTAACAGATATGTATAAGATTTGTACTCTAACTACTATAAGATATTGCTGAGGAAAATTAAAGAAGATTGAAATAAATGAAAAATTGTTCATGGATT

-1188 CAAATATTGTTAAAAATGTCAAATCACCCCAGGTTCATCCAATATGCTTTTTTTTTGGGGGGGGGTAGGAATTGGCAGGTTGATTATTTCATAGTAAAA

-1089 TGCAAAGACCCCACAATAGTCAATATAATATTTACCCAAAAAAATAAAGCAGTATTAGCAAATAGATAAGTAGAACAGAATAGGCCTGCACAYATACAG

-990 GCAATTGACTTTTTTTGACAAAGGTGCCAAGGCTATTATTCAACTGGAGAAGGAAACGTTTTCAACAAATGAAATAGTTTGTGGGGAACAATTAGAAGT

-891 ATGGGAAAAAAAGAAGCCTTGACCCTTACTTAGCTCACACCACAATGAGATTAATCTGAGATATCATAACCTAARTGTAAAAGCTAAAAACACAAAGAT

-792 TCTAAAGGARAACACAGAATATCTCTATGGCTTTAGAGAAGGCAAAGATTTACCAAGGCAATAAATAAAACTTAAAAGAGAAACTGATAAATATCTTTG

-693 TACTCAAAGGGCACTTTTTTTTTTTTTTTTTCCGGCCTTTTATGGCCACATCCGTGGTATATRGAGGCTCCCAGGCTAGGGGTCCAATCTGAGCTGTAG

-594 CTGCGTCCACAGTGACGGGGGATCCGAGCGGCGCCTGTGACCTACACCACAGYTCAGGGAAACGGCAGGATCCTTAACCCACTGAGCGAGGGTAGGGAT

-495 CGAACCTGCGTCCCCATGGATGCTAGTCAGATTCGTTAGCCACTGAGCCACGATGAGAACCCCTCAAAAGACACTTTTAAGAAAATAAGTCACAGCCTG

-396 GGAGAAGATATTTGGAGTGCAGATATGGCAAAACTCCAAGCCAAATCCAACAAACAAACACCAAACTGTCCCACGTGTGTATTTCCTRTAGGTGCATCA

-297 CCTGKCGACCCCACGCCAGGTGGGAATGAGCCCCTGGACGGCCATTTTGGAAGGTGACGTCTTCCTGTAAAGTTAGACKCTGCCCTTCCGACCCACACA

-198 ACTT<GAGGG>AAGTGGTTACACCGCATACATTTGCCAAAACTCAGAACTGTACGCTTAAAATCTGTGCATTTTACTGTATCTCGACCGCTGTAAAAGC

-106 AAAACGAAGAGAAGATGAACMTCAAAAAGCAATCCCCAGGGGTCCTCTTGGGGCGCTCTAGATCCGCGAGCGCCCGCCGGTTGGGGAACCACGCATCCG

-7 AGAAGAAATGAAACCGCGCTGGGAAAGTGAGGGCTCGGGGGTTGGGCCGGTTCCGCCCATTTCCCAACTCGTCGCAGTTTCGATTCTCGGTTCTTCAGC

+93 TACTCCGCCTCCCGGCGCGGGGTGCTTTTTAGGAGACTCCGGGCTTGCCGGGCTTTAGTGCAGCCAGGCGCAGACGAGGCGCGGCCAGAAGCTGAGCCG

+192 GCAGCATGACAGCAGAGCAGCGGCGGAATCTGCACGCTTTCGGGGACTATGTCAGGAAGACTCTCGACCCCACCTTCATCCTGAGCTACATGGCCCCCT

+293 GGTTTAGGGACG

226

Figure IV.5. Sus scrofa PGLYRP1 amplified promoter sequence.

Bolded sequence represents coding region of the PGLYRP1gene with the ATG start codon underlined. No polymorphisms were identified.

-1407 CAACAACTCAACAATCCCAGGAATGGGATTATTTTCTTCCCTTTGCAAATTGATAACAAAAAGGCAAACAACCCACTTTTTTAGTGGGCAATGGAGATT

-1308 AATGCGCGATTGACAAGAGGCAAATCCGAATGCGCAGCAAATAGAAAAATACTCAATCTCCTGAGTGGTCATAAAATTGCCAATTAAAGTCCCAGGAGT

-1209 TCCTGTTGTGGTGCAGTGGGTTCAGAACTCGACTGTCTGCAGTGGCTCAGGTTGCTGGGAAGATGTGGGTTCAATCCCTGGCCAGTGCAATGGGTTAAA

-1110 GGATCCAGCATTGCCCCTGCTAGTAGTGCAATGGGTTAAAGGATCCAGCATTGCCCCTGCTAGTTTGGATTCAATCCCTGCCCCCAGGAACTTCCATAT

-1011 GTCCCAGTGGTGCTTATGTGGAGCTATGAATGAATCAGACATCTTCTAAGGAATCAACTTATGAGTTAGGTGCTTTATATTATCAGCCCACTTTGCATA

-912 TGGGGAAAACTGAGGCACAGAAAGGTTAAGTCAATTGCCTAAGATCACACACTGGAACGTCACCAAAATTTTTTTTTTGTTGTCTTTTTTTTTTTTGCT

-813 ATTTCTTTGGGCCGCTCCCACTGCATATGGAGGTTCCCAGGCTAGGGGTCGAATCGGAGCTGTAGCCACTGACCTACGCCAGAGCCACAGCAACGCGGG

-714 ATCCGAACCGCGTCTGCAACCTACACCACAGCTCACGGCAACGCCGGATCGTTAACCCACTGAGCAAGGGCAGGGACCGAACCCGCAACCTCATGGTTC

-615 CTAGTCGGATTCGTTAACCACTGCGCCACGACGGGAACGCCCCAAAATTTAAATGCAGGCAACCTGGCTCTGAATTTGGGCTCTGAATCAGGCTCCACT

-516 ACCTCCCACGGGTCAGCAACATGACTAGTCCTCTTCCCGCCTCAGTTTACTCAACTGTGAAATGGGCTTCCCAATACTCAGTTCAGTTTGTTGTGAGGG

-417 TTAAGTAACATTGGGCTTAGGCCTGGGCTAAGTGTTTTTTAAAATGGGAGCCTTTGTTTCTTCAGTCCTGGCAAGAAGAAGGGAGAAGGCCAGGGGCCC

-318 CTCTCCTTCCCTTTTTAAGTTCCTGGTGAGCCGTCCAATGCTCCACTGAGAGGGCAGGGCAGAGATCCAGACCCTGGCTCTTCCAAAAACCACTGGGCA

-219 GAGTGCCCACCCCCACCTCCGCGGGGTCAGGACCCCGCCTCTCCTCTCCCGGACTTGACCACACCTCACTCTGTTGCGGCCGGGACCAGAAAAGGAAGC

-120 GATCTGGGGTCCCACCGGGAAGTCCCTGGGGGTGTGATGCAAGCCCTTCCCCCACCAACCCCGCAGATAAAGGCACAGGGCCAGCCTCGAGCTGCCAGG

-21 CGCCTGTGCGCCCTGCCCGCCATGGCCCGCAGCTGCGCGCTGCTCTCCTGGGCCCTCCTCGCCCTCTTCGCCCTCCTCGGGGCTGCTGGGGGAGGTCCG

+79 GCAAACTGCATCCCCATTGTGTCCCGCAGAGAGTG

227

Figure IV.6. Sus scrofa PGLYRP2 amplified promoter sequence.

Bolded sequence represents coding region of the PGLYRP2 gene with the ATG start codon underlined. No polymorphisms were identified.

-1401 CCTGACCCCAAATCCTTAGAAACTGGGACTTGGAGGAGATTTCCTCAGAATCTGCTGGGGAGTAACTTCTATTCCCCCTTCACCCGCTTTAGCAACCAA

-1302 CTCCCTGAGCCCCTCAGCTTTATTCTAGACCATTCTGGGGCCCAGAAAGAAGACACTATCTGAGCAGGCCCCTGGGAATCCCAGGCCTGGCTCAGCCTG

-1203 GGCATTCCCAGGCCCGCCCAGGGCCCGCCCTGTGCTAAGTGCCCAACCTGGTGGGTCTCCTGGAAAATCCCCAGGCTAGTTTCCAGATGGGAGGTCCAC

-1104 AGTGAAGCAATTTACACGGCAGCCCCAGCCACTTTGAGCCCATCCCACCCGACACTAGATAAAGGGGAGGAGGACTGTCTTCAGCAGGACCTCACCACA

-1005 GGCACCAGAGGAAGAGGAGGACCCCTCACTGCCAACACAGGTGAGCCCAGAAGTCAACTCTGGGGACAAAGCCAGGGTCCCAAATGCTCCAATCCAATT

-906 CCTGCTCTTAGCTACCTCTGGTGGCTTAGGATCCAGAGCTGGAACAGGATGAGAGGTGACACCTCCAGGTCCCCCTACTCTCTGAGCAGACTTCAGCAA

-807 AAGCAATCCTTGGTCCCTGCACCCATCCCCTGCCTGAGGCTGAAATGCTGGCAGCAAAGAAGGCAGGAGGTGGCACCAACTTCAGGCCTCTCCTTCTCT

-708 CCCCACCCCAAGTACAGCCAGTCTTACCAGTCAGGCAGGCACCTGAGAGGCCCCTCTGGTGGCCAGCAGCAGCTATAGAACTATCACCATAGGAAGTAT

-609 GGATTGCTGGATTGAACTCAGTCTACCTCTCCTGGGAAATGGGCAGAGTTTGCTGGAGTGTGAACTACCTGGTTTCCAGGCCTTTTTTTTTTTTTTTTT

-510 TTTTTTTTGGTTTTTAGGGCTGCACTTGTGGCATATGGAGTTGCCCAGCCTAGGGGTCAAATTGGTGCTGCTTCTAGTCTATGCCACAGCCACAGCAAT

-411 GCAGGATCCAAGCTGTGCCTGCAACCTACACCACAGCTCATGGCAATGCTGGATCATTAACCCATTTAGCAAGGCCAGGGATTGAACTTGCATCCTCAT

-312 GGATACTAGTTGGGTACATTACCACTGAGCCACAATGGGAACTCTTCCAGGCCACTTATGAAATGAGGATTGGCTTACTGACCCTTGACCTCAGCCTGG

-213 AAGGGAGAGGATAGAATGGGGGAGCCCCTGAGATCCAGATGGCCTTGAGCCAGGGCACTCTGTACACATTCCCCCGCTGCCTCCCGCCCACAGCTCTGC

-114 AAGAGGCAGCGTGTCATTCACCACTGGACTTTGACAGCAGCCAAAGGCACAACTCAATTCTCCATGCGTGTCTCCTTTCAGCTACACCGAGGTCTCCAC

-15 TGAGGTCAACCAGATATGTCCCCTGGAAACTGGAAGACCACAATGGTGGTCCGGGGTATCCTGTTGATCCTGTATGGATTGCTTCTGCAGCCGGAGCCA

+85 GGAACAGGTGAGC

Documents

Constitutive Variation in Hepatic Expression of Porcine Innate