Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Maternal care and Gene -
Environment Interactions Defining Development
Michael J Meaney
PhD
James McGill ProfessorDept. Psychiatry
McGill UniversityDouglas Hospital Research Centre
The development of an individual is an active process of adaptation that occurs within a social and economic context:
•
To resource (food, shelter, safety) availability.
•
To social interactions.
•
To independence from the parent.
Early experience
AbuseFamily strifeEmotional neglectHarsh discipline
Health Risks
DepressionDrug abuseAnxietyDiabetesHeart diseaseObesity
Mechanism?
Developmental Origins of Adult Disease
Early experience
AbuseFamily strifeEmotional neglectHarsh discipline
Health Risks
DepressionDrug abuseAnxietyDiabetesHeart diseaseObesity
Individual differencesin neural and endocrine responses to stress (defensive responses)
Stress Diathesis Models
Early experience
AbuseFamily strifeEmotional neglectHarsh discipline
Health Risks
DepressionDrug abuseAnxietyDiabetesHeart diseaseObesity
Individual differencesin neural and endocrine responses to stress
Poverty
Early experience
AbuseFamily strifeEmotional neglectHarsh discipline
DepressionDrug AbuseAnxietyObesityDiabetesHeart Disease
Poverty
Effects of poverty on emotional and cognitive development are mediated by parental factors (Conger, McLloyd, Eisenberg).
Poverty
Maternalemotionaldistress
Parenting
Childbehaviouralproblems
Linver, Brooks-Gunn & Kohen
Dev Psychol
2002; same model predicts child cortisol
levels (Lupien, McEwen, Meaney
Biol
Psychiatry 2000)
Nutrient Supply
Mate Quality
Violence
Infection
Population density
Parentalinvestment
Defensive Strategies
Foraging/Metabolism
Reproductive Strategies
Environmental Parental Developmentalsignal mediation outcome
Robert Hinde: Evolution has shaped the young to use parental signals as a ‘forecast’
of the quality of the environment
into which they have been born. For most species, there isno single, optimal phenotype.
Evolutionary biology -
Maternal effects
Environmentaladversity -mother
Mother -
offspringinteractions
Programming of defensive responses in offspring
Over her lifespan?
• Seed
•
Propulagate
• Yolk
• Uterine
•
Maternal care
Evolutionary Biology: Maternal Effects
Defense to snake predation in skink lizards
Most frequent prey
• smaller•
shorter tails
•
less reactive to snake cues
If mother has been exposed to the scent of apredatory snake then offspring are larger, withlonger tails and ….
Control Perfume Snake0
1
2
3
4
Response to snake odours
Tong
ue-F
lick
Offspringare significantlylarger and withlonger tails
Scanning electron micrograph showing typical and predator-induced morphs of Daphnia cucullata of the same clone.
Predatorexposed
Control
Inducible defenses
25
15
20
10
30
K C
C C
N A K+
Agrawal
et al. Nature 1999
Rel
ativ
e he
lmet
size
Rel
ativ
e he
lmet
size
Nutrient Supply
Mate Quality
Violence
Infection
Population density
Parentalinvestment
Defensive Strategies
Foraging/Metabolism
Reproductive Strategies
Environmental Parental Developmentalsignal mediation outcome
Robert Hinde: Evolution has shaped the young to use parental signals as a ‘forecast’
of the quality of the environment
into which they have been born. For most species, there isno single, optimal phenotype.
Evolutionary biology -
Maternal effects
Summary
•
Parental care affects the activity ofgenes in the brain that regulate stressresponses, neural development and reproduction.
•
This parental effect involves a forma “plasticity”
at the level of the DNA.
Epigenetics: Any functional change in the genome thatdoes not involve an alteration of DNA sequence.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
C T A C G T A C T C G G A A T C T C G
Genetic code is defined by the sequence of four nucleotides that produce proteins and other molecules that serve cell function.
Protein
Epigenetic effects refer to modifications of the chemistry of the DNA, but not
to a change of sequence. Epigenetics alters the activity of the
gene, but not its function.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
C T A C G T A C T C G G A A T C T C G
Genetic code is defined by the sequence of four nucleotides that produce proteins and other molecules that serve cell function.
Protein
Epigenetic effects refer to modifications of the chemistry of the DNA, but not
to a change of sequence. Epigenetics alters the activity of the
gene, but not its function.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
•
Epigenetic effects refers to modifications of thechemistry of the DNA, but not
to a change of sequence.
•
Epigenetics alters the activity of the gene, but not its function.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
•
Epigenetic effects refers to modifications of thechemistry of the DNA, but not
to a change of sequence.
•
Epigenetics alters the activity of the gene, but not its function.
•
DNA methylation: The addition of a methyl group onto a cytosine.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
•
Epigenetic effects refers to modifications of thechemistry of the DNA, but not
to a change of sequence.
•
Epigenetics alters the activity of the gene, but not its function.
•
DNA methylation: The addition of a methyl group onto a cytosine.
•
DNA methylation is chemically very stable (potentially lasting
forthe life of the organism).
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
•
Epigenetic effects refers to modifications of thechemistry of the DNA, but not
to a change of sequence.
•
Epigenetics alters the activity of the gene, but not its function.
•
DNA methylation: The addition of a methyl group onto a cytosine.
•
DNA methylation is chemically very stable (potentially lasting
forthe life of the organism).
•
DNA methylation silences gene expression.
Nucleosome core particle: ribbon traces for the 146-bp DNA phosphodiester backbones (brown and turquoise) and eight histone protein chains (Luger et
al. Nature 1997).
+ -
Prevents TFbinding to DNA
TF binding involvesalteration of
chromatin structure
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
C T A C G T A C T C G G A A T C T C G
Genetic code is defined by the sequence of four nucleotides that produce proteins and other molecules that serve cell function.
RNAs, proteins
Epigenetic effects refer to modifications of the chemistry of the DNA, but not
to a change of sequence. Epigenetics alters the activity of the
gene, but not its function.
SIN
SIN
CH3
CH3
CH3
CH3 MECP2
HDACCH3
CH3 MECP2
DNA Methylation can inhibit gene expressionby blocking transcription factors binding
HDAC HDAC: Histone
deacetylase
Methylated DNAbinding protein
Naturally-occurringvariations in maternal care
Expression of specific genesin brain regions
HPA function
Stable individual differencesin stress reactivity
Maternal licking/grooming
Source of tactile stimulation/nurturance: Enhances Source of tactile stimulation/nurturance: Enhances activity of endocrine systems (e.g., GH/IGF) that activity of endocrine systems (e.g., GH/IGF) that promote somatic growth, suppresses those promote somatic growth, suppresses those (glucocorticoids) that inhibit growth(glucocorticoids) that inhibit growth
Variations in maternal careVariations in maternal care
Freq
uenc
y co
unt
% Licking/grooming
Low LGMean -
1SDHigh LG
Mean + 1SD
HighLow
Days of Age
Lick
ing/
groo
min
g
Variations in maternal care X DaysVariations in maternal care X Days
* No differencesin time with pups
Are these naturallyAre these naturally--occurring variationsoccurring variationsin maternal behaviour associated within maternal behaviour associated with
the development of individual differencesthe development of individual differencesin endocrine and behavioural responses in endocrine and behavioural responses
to stress?to stress?
* Effects hold for both males and females
fetal postnatal peripubertal adulthood
Maternal care Outcomes
autonomicautonomicoutputoutput
(Noradrenaline)(Noradrenaline)HPA outputHPA output
(glucocorticoids)(glucocorticoids)
(NA)
Baso-lateral
complex
Centraln.
mPFC
Locus coer.PB nNTSP
VN
Sensoryinput
(Stressor)
Hippocampus BNST
autonomicautonomicoutputoutputHPA outputHPA output
(NA)
Baso-lateral
complex
Centraln.
mPFC
Locus coer.PB nNTSP
VN
Sensoryinput
(Stressor)
Hippocampus BNSTGCrec
GlucocorticoidReceptor
Hypothalamus
Pituitary
Adrenals
Hippocampus
Glucocorticoids
Stress
(-)
CRF
ACTH
CRF: corticotropin releasing factor. ACTH: adrenocorticotropin
Hypothalamus
Pituitary
Adrenals
Hippocampus
Glucocorticoids
(-)
CRF
ACTH
(-)
Hypothalamus
Pituitary
Adrenals
Hippocampus
Glucocorticoids
(-)
CRF
ACTH
(-)
Individual differences in glucocorticoid receptorlevels lead to altered pituitary-adrenal responses
to stress
Hypothalamus
Pituitary
Adrenals
High LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Hypothalamus
Pituitary
Adrenals
Low LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Individual differences in glucocorticoid receptorlevels lead to altered pituitary-adrenal responses
to stress
Adult offspring of High LG mothers show more modest HPA responses to stress
Pre S10 S20 P20 P40 P60 P1200
200
400
600
800
1000High LGLow LG
Plas
ma
AC
TH (p
g/m
l)
Pre 10 20 40 60 80 1000
10
20
30
40
50
60
70
80High LGLow LG
Cor
ticos
tero
ne (µ
g/dl
)
Intra-hippocampal infusion of a GR antagonist completely eliminates the maternal effect on HPA responses to stress
Hypothalamus
Pituitary
Adrenals
High LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Hypothalamus
Pituitary
Adrenals
Low LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Individual differences in glucocorticoid receptorlevels lead to altered pituitary-adrenal responses
to stress
Adaptive advantages of increased stress reactivity(Central CRF systems, HPA axis, Catechols)
• Increased resistance to sepsis (infection).• Increased resistance to famine.• Decreased mortality due to aggressive conflict.
Poverty: Pathogens, nutritional deprivation and violence
Hypothalamus
Pituitary
Adrenals
High LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Hypothalamus
Pituitary
Adrenals
Low LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Individual differences in glucocorticoid receptorlevels lead to altered pituitary-adrenal responses
to stress
Hypothalamus
Pituitary
Adrenals
High LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Hypothalamus
Pituitary
Adrenals
Low LG offspring
Glucocorticoids
(-)
CRF
ACTH
(-)
Cross-fostering reveals evidence for direct, postnataleffects of maternal care
How might maternal licking/groomingregulate hippocampal glucocorticoid
receptor gene activity and HPA function?
And how do these effects persist over the lifespan
of the offspring?
SignalReceptor
Extracellular signalMaternalMaternalCareCare
DNA
Transcription
Factors
Intracellular signal
gene
Relevant gene -
environment interaction
cAMP
NGFI-A
5-HT7
rec
5-HTTactile stimulationTactile stimulation(maternal LG)(maternal LG)
GR gene
PKA
(T3)
(H-P-T)
Transcription
Factor
Summary of in vivo and in vitro studies
CTL5-HT
7 15 30 500
50100150200250
Days in CultureG
R le
velscAMP
NGFI-A
5-HT7
rec
5-HT
GR gene
PKA
Represents period of 5-HT exposure
*
1.5
1.0
0.5
0.0
NGFI-A mRNA levels
cAMP
NGFI-A
5-HT7
rec
5-HT
GR gene
PKA
Day 6 pups
Low LG High LG
*0.9
0.6
0.3
0.0
NGFI-A mRNA (stroking)
R/S R/C HC
Ctl 5-HT 5-HT0
1
2
3
4
+ NGFI-A antisense
GR
ir (R
OD
)
*
Weaver et al., 2006
In vitro (primary hippocampal neuronal cultures) studies
cAMP
NGFI-A
5-HT7
rec
5-HT
GR gene
PKA
What are the relevantgenomic targets?
Clone the 5’ untranslatedregion of the rat hippocampal glucocorticoid receptor gene
cAMP
NGFI-A
5-HT7
rec
5-HT
GR gene
PKA
Gene organization
Non-coding, regulatoryregion (contains enhancers,
repressors, etc.).
Coding regionresponsible for protein
synthesis.
(+ or -)
Clone the 5’ untranslated region of the rat hippocampal glucocorticoid receptor gene
Glucocorticoid receptor gene
(~110 kb)
1 2 3 4 5 6 7 8 9 101112 2 3 4
5 6 78 9
Variable exon 1 region Constant region
5’ 3’
(McCormick et al. Mol Endo 2000)
Transfection studies with promoter-reporter constructs reveal exon 17
sequence has considerable transactivational capacity.
Critical forHippocampal
GR
1 2 3 4 5 6 7 8 9 101112 2 3 4
5 6 78 9
Variable exon 1 region Constant region
5’ 3’
1681 ccc1741 ctctgctagt gtgacacact t1cg2cgcaact c3cgcagttgg 4cggg5cg6cgga ccacccctg7c1801 ggctctgc8cg gctggctgtc accct9cgggg gctctggctg c10cgaccca11cg ggg12cgggct1861 c13cgag14cggtt ccaagcct15cg gagtggg16cg gggg17cgggag ggagcctggg agaa
DNA sites that regulate glucocorticoid receptor gene
NGFI-A
GR Promoter 17 Sequence
1 2 3 4 5 6 7 8 9 101112 2 3 4
5 6 78 9
5’ 3’
NGFI-A binding to the GR(17
) promoterin neonates
**
00.10.20.30.40.50.60.70.80.9
Ant
ibod
y/in
put (
RO
D) 1.0
NGFI-A
cAMP
NGFI-A
5-HT7
rec
5-HT
GR gene
PKA
…..
Exon 1 (Noncoding region) Exons 2- 9 Coding region
5’ 3’
(+)
Glucocorticoid receptor mRNA
Glucocorticoid receptor protein
Offspring of High LG mothers
1177
NGFI-A
…..
Exon 1 (Noncoding region) Exons 2- 9 Coding region
5’ 3’
(+)
Glucocorticoid receptor mRNA
Glucocorticoid receptor protein
Offspring of High LG mothers
1177
NGFI-A
*
1.5
1.0
0.5
0.0
1.5
1.0
0.5
0.0
Pup Adult
NGFI-A levels
So, while increased levels of NGFI-A can explain the increased activity of the glucocorticoid receptor genein the pup, it does not explain why the difference is still observed in adult animals?
…..
Exon 1 (Noncoding region) Exons 2- 9 Coding region
5’ 3’
(+)
Glucocorticoid receptor mRNA
Glucocorticoid receptor protein
Offspring of High LG mothers
1177
NGFI-A
Stable modificationof the DNA????
•
DNA methylation occurs at cytosines.•
DNA methylation is chemically very stable.
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
CH3
CH3
CH3
CH3 MECP2
HDACCH3
CH3 MECP2
DNA Methylation can inhibit gene expressionby blocking transcription factors binding
HDAC HDAC: Histone
deacetylase
Methylated DNAbinding protein
1681 ccc1741 ctctgctagt gtgacacact t1cg2cgcaact c3cgcagttgg 4cggg5cg6cgga ccacccctg7c1801 ggctctgc8cg gctggctgtc accct9cgggg gctctggctg c10cgaccca11cg ggg12cgggct1861 c13cgag14cggtt ccaagcct15cg gagtggg16cg gggg17cgggag ggagcctggg agaa
DNA sites that regulate glucocorticoid receptor gene
NGFI-A
GR Promoter 17 Sequence
1 2 3 4 5 6 7 8 9 101112 2 3 4
5 6 78 9
5’ 3’
5’…T G C G G G G G C G G G G ……
3’
5’…T G C G G G G G C G G G G …….3’CH3
CH3
5’…T G C G G G G G C G G G G …….3’
CH3
CH3
5’…T G C G G G G G C G G G G ……
3’
(no methylation)
(methylated only at 3’; High LG)
(methylated only at 5’)
(methylated at both 5’
and 3’; Low LG)
NGFI-A binding to ….
(High LG)
(Low LG)
*
1.5
1.0
0.5
0.0
1.5
1.0
0.5
0.0
Pup Adult
NGFI-A levels
So while levels of NGFI-A are similar in animals rearedby High or Low licking/grooming mothers, the NGFI-A
site in the adult offspring of Low LG mothers is methylated and therefore cannot interact with NGFI-A.
But….
Maternal Care
Glucocorticoid receptorgene expression
CRF expression
Individual differences in stress reactivity
GC feedbacksensitivity
Differential methylation of GR promoter… differences in NGFI-A
binding.
cAMP
NGFI-A
5-HT7
rec
5-HTTactile stimulationTactile stimulation(maternal LG)(maternal LG)
GR gene
PKA
(T3)
(H-P-T)
Do these ‘maternal’
signals alter the methylationof the exon 17 GR promoter?
Do comparable processes occur in humans?
•
Post-mortem studies of hippocampus.
•
Samples from suicide victims/controls.
•
QSBB (Gustavo Turecki) -
forensicphenotyping.
•
Human exon 1F promoter (Turner & Muller, J Molec Endo, 2005)
Hippocampal samples from humans
•
Human brain bank (suicide victims vs controls).
•
All suicide victims (and none of the controls)experienced verified abuse in childhood.
Human glucocorticoid receptor gene
A B C D E F G H I J
2 3 4 5 6 7 8 9
Variable exon 1 region Constant region
5’ 3’
Human glucocorticoid receptor gene
A B C D E F G H I J
2 3 4 5 6 7 8 9
Variable exon 1 region Constant region
5’ 3’
Control Suicide0.0
0.5
1.0
1.5GRtotal
GR
mR
NA
Control Suicide0.0
0.3
0.6
0.9
1.2 GR1F
GR
1-F
var
iant
s
McGowan et al. PlosOne 2008, Nature Neuroscience 2009
Suicide vs abuse -
GR expression
GRtotal
GR
mR
NA
/GA
PDH
(log
con
c.)
Control Suicide Suicide-
Abuse + Abuse
0.0
0.4
0.8
1.2
*
GR
-1F
mR
NA
/GA
PDH
(log
con
c.)
Control Suicide Suicide-
Abuse + Abuse
0.0
0.5
1.0
1.5
*
McGowan et al. PlosOne 2008, Nature Neuroscience 2009
GR
1-F
CpG
Met
hyla
tion
(%)
Control Suicide Suicide-
Abuse + Abuse
0
20
40
60 *
0
20
40
60
30 31 32CpG sites
Suicide vs abuse -
CpG methylation
McGowan et al. PlosOne 2008, Nature Neuroscience 2009
Control NGFI-A expression
Co-transfection studies (NGFI-A vector w/human GR exon 1F-luciferase construct)
0
2000
4000
6000
8000
10000
12000
14000
Luci
fera
se a
ctiv
ity
mPlasmid nmPlasmid Antisense
McGowan et al. PlosOne 2008, Nature Neuroscience 2009
C T A C G T A C T C G G A A T C T C GCH3CH3CH3
DNA methylation serves as an interface between the dynamic environment and the fixed genome
DNA methylation serves to imprint social factors, such as maternal behavior, upon the offspring’s genome.
cAMP
NGFI-A
5-HT7
receptor
5-HTTactile stimulationTactile stimulation(maternal LG)(maternal LG)
Synaptic plasticity
PKA CBP