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Special Topic

Human Genomics and Microarrays:Implications for the Plastic Surgeon Jana Cole, M.D., and Frank Isik, M.D.Seattle, Wash.

The Human Genome Project was launched in 1989 inan effort to sequence the entire span of human DNA. Although coding sequences are important in identifyingmutations, the static order of DNA does not explain how a cell or organism may respond to normal and abnormalbiological processes. By examining the mRNA content of a cell, researchers can determine which genes are beingactivated in response to a stimulus.

Traditional methods in molecular biology generally work on a one gene: one experiment basis, which meansthat thethroughput is very limited andthe wholepictureof gene function is hard to obtain. To study each of the60,000 to 80,000 genes in the human genome under eachbiological circumstance is not practical. Recently, mi-croarrays (also known as gene or DNA chips) haveemerged; these allow for the simultaneous determinationof expression for thousands of genes and analysis of ge-nome-wide mRNA expression.

The purpose of this article is twofold: first, to provide

the clinical plastic surgeon with a working knowledge andunderstanding of the fields of genomics, microarrays, andbioinformatics and second, to present a case to illustratehow these technologies can be applied in the study of wound healing. ( Plast. Reconstr. Surg. 110: 849, 2002.)

A phenomenal scientific achievement oc-curred 40 years ago: the chemical structure of DNA was cracked by Watson and Crick. 1 Inthe year 2000, another scientific milestone wasachieved. On June 26, researchers told the world that they had identified the order of all 3

billion chemical units that make up the humangenome. 2 The first draft sequence of the entirehuman chromosome set was identified. Al-though the precise number of human chromo-somes was still under debate when Watson andCrick 1 made their discovery, we now know that there are 46 human chromosomes, which be-tween them house 3 billion base pairs of DNA and encode about 60,000 to 80,000 proteins.

The effort to sequence the entire span of human DNA, the Human Genome Project, waslaunched in 1989 as a consortium between theNational Institutes of Health and the Depart-ment of Energy. The Human Genome Project served to develop technologies for genomicanalysis, to examine the ethical, legal, and so-cial implications of human genetics research,and to train scientists to use these tools andresources to pursue biological studies that willimprove human health.

At first glance, the sequencing of the humangenome and the related technology that hasemerged do not seem to affect the practicingplastic surgeon. Many laboratory discoveriesimpact very little on our day-to-day practice.The discovery of a promising endogenous mol-ecule or application of a novel technique ini-tially seems to be a panacea for many clinicalproblems, but then does not change our prac-tice as initially hoped and hyped.

The purpose of this article is twofold: first, toprovide the clinical plastic surgeon with a work-ing knowledge and understanding of the fieldsof genomics, microarrays, and bioinformaticsand second, to present a case to illustrate how these technologies can be applied in the study of wound healing.

THE W ORKINGS OF A CELL

Genes and their products (i.e., RNA andproteins) are thought to function in a compli-cated and orchestrated way to create the mys-tery of life. The human body begins as a fusionproduct of two cells, the egg and the sperm.The successive division of the fusion product results in the formation of the adult organism,

From the Division of Plastic Surgery, University of Washington School of Medicine. Received for publication June 25, 2001; revised November19, 2001.

DOI: 10.1097/01.PRS.0000019918.86678.91

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which contains approximately 10 14 cells. Al-though each adult cell preserves the entireDNA content of the original single cell, theprogeny cells have become specialized in func-tion (i.e., differentiated).

The cell differentiation pathway is dictatedby the restricted spatial and temporal expres-sion of specific genes that are coded for by theDNA. Which genes or clusters of genes inducedifferentiation to a particular cell type, such asa chondrocyte or adipocyte, are key questionsnow being asked by many investigators andcompanies. In addition, the response of differ-entiated cells to an external stimulus such astissue injury depends on the expression of dif-ferent clusters of genes at different times. 35 Asresearch improves and matures our compre-hension of cellular differentiation and cellular

response mechanisms, we will gain insight intothe causes of many congenital anomalies andcancer and possibly even develop therapeuticstrategies to treat them.

As a brief review, we will go over the neces-sary definition of terms and cell function. Thenucleus of a human cell contains 23 pairs of chromosomes, with each chromosome being

made up of DNA molecules. DNA moleculesconsist of two long chains held together by complementary base pairs. Each chain is along, unbranched polymer composed of only four types of subunits or bases. These are thedeoxyribonucleotides containing adenine (A),guanine (G), cytosine (C), and thymidine (T).There is complementary base pairing between A and T and between C and G. This means that each strand of the DNA molecule is a mirrorimage of the other and the molecule exists as adouble helix. The order in which these sub-units are linked together represents a blue-print for the cell, providing all the necessary information to construct a cell or even gener-ate a clone of an individual (Fig. 1). The infor-mation contained in the chain of the DNA molecule is read in triplicate (e.g., AGC TAG

ATG. . .), with each possible triplicate combi-nation (codon) coding for one of the 20 aminoacids, the building blocks of proteins. Con-tained within the long chain of the DNA mol-ecule are short segments that code for pro-teins. A protein is made by a series of stepscalled transcription and translation. The blue-print for making the protein resides on the

FIG. 1. Illustration of the transfer of information from DNA to protein. This proceeds by means of mRNA. During transcription, one strand on the DNA serves as a template for the new mRNA. This transfer of information is accomplished by complementary basepairing between thebases A and U and C and G. The mRNA can cross the nuclear membrane into the cytoplasm.The mRNA then binds to ribosomes (location where the protein is made), which translate theinformation in the mRNA into protein. This step is called translation. The mRNA is then usually degraded after the protein is produced.

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chromosome in the nucleus, but the proteinmachinery resides in the cytoplasm, and they are separated by the nuclear membrane. Thetransfer of information from DNA to proteinproceeds by means of an RNA intermediatecalled messenger RNA (mRNA).

Both DNA and RNA are linear polymers of nucleotides, but they differ in three ways. Thesugar phosphate backbone in RNA containsribose instead of deoxyribose, RNA containsthe base uracil (U) instead of thymidine (T),and RNA exists as a single strand instead of adouble helix. During transcription, one strandon the DNA serves as a template for the new mRNA. The mRNA is again transcribed by complementary base pairing (A 3 U andC3 G) and provides a mirror image of theDNA template. The mRNA can cross the nu-

clear membrane into the cytoplasm. ThemRNA then binds to ribosomes (location where the protein is made), which translate theinformation in the mRNA into protein. Thisstep is called translation. The mRNA is usually degraded after the protein is produced. Al-though critical for the function of a cell, mes-senger RNA does not have a function outsidethe nucleus other than to transport the codenecessary to build the protein. Protein is theultimate molecule that provides structure andfunction for the cell.

The vast majority of the DNA in a cell, evenif the cell is actively proliferating and migrat-ing, is inactive. In other words, only a smallfraction of the 60,000 to 80,000 genes are be-ing transcribed into mRNA. Because mRNA isoften rapidly degraded shortly after the pro-

tein is made, the mRNA content of a cell at any given time represents what that cell is doing orresponding to at that moment. This is an im-portant point that is exploited by the microar-ray technology.

GENOMICS AND MICROARRAYSThe term genome refers to all the genetic

material in all the chromosomes of a particularorganism. For us to understand the molecularbasis of health and disease, we need to know more than the coding sequence of the ge-nome. Although coding sequences are impor-tant in identifying mutations linked to certaincancers, the static order of the DNA does not tell us how a cell or organism may respond tonormal and abnormal biological processes. Weneed to know which gene products are made in

biological processes that affect human healthand disease, from embryonic development tocancer development. The best method to in- vestigate this currently is by examining themRNA content of a cell.

Traditional methods in molecular biology gen-erally work on a one gene: one experiment basis, which means that the throughput is very limited and the whole picture of gene functionis hard to obtain. To study each of the 60,000 to80,000 genes individually under each biologicalcircumstance is not practical. Recently, newer

high-throughput techniques have emerged, suchas differential display, 6 serial analysis of gene ex-pression (SAGE), 7 and microarrays (also knownas gene or DNA chips). 8 Of these high-through-put techniques, microarrays are much moreefficient; they allow for the simultaneous deter-

FIG. 2. This diagram demonstrates the attraction of certain nucleotides to each other (A 3 T and G 3 C) and how, over a longstretchof DNA,the sequence alignment becomescritical forhybridization (reformingof thedoublehelix)to occur.In microarray experiments, known sequences are immobilized on a solid surface. The labeledsamplebathes the microarray. If there is sufficient match between two complementary sequences, then a stable duplex will form. The rate of double helix formation duringhybridization is limited by the rate at which the two complementary nucleic acids happen to collide, which depends on theirconcentration in the solution. Hybridization rates can therefore be used to determine the concentration of any desired RNA or DNA sequence in a mixture.

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mination of expression for thousands of genes,and they analyze genome-wide patterns of mRNA expression. We will focus our discussionon this technology.

Microarrays

Complementary base-pairing (i.e., A 3 T andG3 C for DNA; A 3 U and G 3 C for RNA) orhybridization is the underlying principle of DNA microarrays (Fig. 2). The natural pairingof certain nucleotides, for example, adenine with thymidine and guanine with cytosine,forms the tight duplex of DNA. 9 An array means an orderly arrangement. In microarrays,the premise is to have known and unique com-plementary DNA (cDNA) sequences immobi-lized on a support surface while the radiola-beled sample (mRNA or DNA) passes overeach spot, as shown in Figure 2. If there is amatching mRNA for that immobilized cDNA,

then the labeled mRNA will hybridize (form adouble helix) to that spot. Depending on thelabeling method, the spot will then either flu-oresce or be radioactive, which is easily de-tected by scanning techniques. Because thereis a known amount of cDNA spotted, theamount of fluorescence or radioactivity can bequantified.

There are two competing formats for themicroarrays. In one format, cDNA (each rep-resenting a gene 500 to 5000 bases long) isimmobilized to a solid surface such as glass by high-speed robotics. This method, traditionally called cDNA microarray, was developed princi-pally at Stanford University. 8,10 14 In the com-peting format, an array of oligonucleotides (20to 25 oligos) is synthesized either in situ (on-chip) or by conventional synthesis followed by on-chip immobilization. 15 This method, histor-ically called DNA chips, was developed at Af-

FIG. 3 . (Above, left ) Example of a nylon microarray (from Research Genetics) that contains 4000 known human cDNA sequences. Each spot represents a unique gene sequence. ( Above, right and below, left ) cDNA microarray membranes afterhybridization with two different radiolabeled mRNA sources and scanned by phosphorimager. Darker spots indicate increasedgene expression. ( Below,right ) Image generated by the Pathways software program (Research Genetics) comparing the twomRNA samples. Genes that predominate in sample one are shown in red. Genes that predominate in sample two are shown in green.Those genes with equal expression in both samples are shown in yellow.



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fymetrix , Inc., which sells its products underthe GeneChip trademark. In either case, thearray is exposed to labeled DNA or mRNA samples, hybridized, scanned, and analyzed todetermine the identity and abundance of eachgene in the sample.

There are two major applications for eithermicroarray technology: (1) identification of DNA sequence (gene or gene mutation) and(2) determination of mRNA expression levelor abundance. In the first application, specialsets of microarrays have been constructed that are specific in identifying certain gene muta-tions. For instance, the BRCA1 and BRCA2 gene mutations have been linked to the devel-opment of ovarian and breast cancer. Patients who carry the mutation can be identified rap-idly using specially constructed cDNA microar-rays that have the immobilized BRCA1 andBRCA2 gene mutations and the nonmutatedBRCA1 and BRCA2 genes. 16,17 If patients arenot carriers, then their DNA will not hybridizeto the BRCA1 and BRCA2 gene mutation spots,only to the nonmutated spots. This methodrequires obtaining a blood sample or buccalswab to obtain the genomic DNA. Because ev-ery cell in the body contains the same DNA,identification of the inheritable mutation inany cell type identifies the patient as a carrierof the mutation. This allows rapid screening of

the patient s DNA without having to sequencetheir DNA. In addition, several other microar-rays have been constructed for the identifica-tion of mutations associated with many othertypes of cancers. 18 25

The other application of microarrays in- volves monitoring the mRNA expression of thousands of genes simultaneously. Unlike theprevious application of microarrays that as-sayed the patient s genomic DNA content andsequence, expression arrays assay the patient s,or cells, mRNA content. This allows for mas-

sively parallel gene expression and gene discov-ery studies, which will be discussed later in thisarticle. A single experiment can provide infor-mation on thousands of genes simultaneously (i.e., which genes are increased or decreased inspecific biological processes); this is a dramaticincrease in throughput over the one gene: oneexperiment method. Although currently re-stricted to several thousands of genes, this tech-nology in the near future promises to monitorthe entire human genome on a single mem-brane or glass slide so that researchers candetermine the expression of all genes during

any biological process. Microarrays represent the biological equivalent of the integratedchip.

Bioinformatics

The generation of such vast volumes of datarequires specialized methods to catalogue,group, analyze, and interpret the biologicaldata. The field of bioinformatics is defined asthe application of computers, databases, andcomputational models to the management of this enormous amount of biological informa-tion. In general, most of the analysis tools inuse today use computational methods to group(cluster) genes or experiments with similarprofiles of changes in expression levels. 26 Theassumption is that by distinguishing genes that behave similarly, it is possible to gain insight into shared regulatory aspects or shared func-tions by the cluster of genes.

Hierarchical clustering is the most com-monly used tool in gene expression analysis.Pairwise matrices can be used to identify genessharing a similar expression pattern acrossmultiple experiments. In one such method, all values are paired, and modified Pearson corre-lations are calculated for each possible pairwisecombination and used in distance matrices.This allows hierarchical clustering of groups of genes that behave most similarly. Cluster, a

hierarchical clustering-based algorithm is oneof the most common tools used to analyzemicroarray data. 26

Self-organizing maps are ideally suited forexploratory data analysis. 27 They are consid-ered superior to hierarchical clustering whenanalyzing messy data that contains outliersand irrelevant variables. The basic concept isthat you impose a partial structure on the dataand then adjust the structure according to thedata. The input data are the raw expression values obtained from the microarray experi-

ments. The output is a series of maps repre-senting similar patterns of gene expression.The infancy of high-throughput gene analy-

sis is reflected in the analytical tools used todecipher the voluminous information. With ei-ther method, the analysis is based on the sim-ple premise that if it is variable, perhaps it isimportant, and if a group of genes are similarly variable, perhaps they all share a similar func-tion. Although simple observations about therelative expression of genes in different samplegroups will not lead to conclusions about phys-iologic or pathologic processes, they can be



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used to generate hypothesis-driven mechanis-tic experiments that define the function of specific genes in specific biological processes.It is these studies that will ultimately validatethe importance of expression profiling by mi-croarrays. Currently, microarrays are largely used as a screening tool, as exemplified in theexample below.

CLINICAL CORRELATION

In our laboratory, we have applied cDNA microarray technology to the study of woundhealing. We performed a series of experimentsusing microarrays to determine the gene ex-pression profile of normal human skin, 3acutely wounded skin, 4 and hypertrophic scar-ring. 5 In the sequence to follow, we will providea step-by-step illustration of how the techniquecan be used, and we will highlight some of theanalyses that can identify which genes may berelevant to normal wound healing.

Step 1

With Institutional Review Board approval, weobtained skin samples from a healthy woman who was undergoing elective breast reconstruc-tion 10 years after a mastectomy. Using an 8mm punch, we obtained normal skin samplesand injured skin samples at 30 minutes, 1 hour,2 hours, 4 hours, and 1 month after wounding

from the latissimus dorsi donor site. The1-month biopsy was obtained from a small de-hiscence of the donor site and represents anopen epithelializing wound.

Step 2

The mRNA from intact skin was extracted,reverse-transcribed into 33 P-radiolabeledcDNA, and hybridized onto high-density cDNA microarray membranes of 4000 genes (Fig. 3,above , left ). This membrane was then scannedon a phosphorimager to produce the raw im-

ages seen in Figure 3 ( above, right , and below,left ).

Step 3

The two images were then analyzed by thePathways software program (Research Genet-ics, Inc.) to determine the intensity of eachcDNA on each membrane; intensity correlates with abundance. The radioactive intensities be-tween the two samples can then be compared(Fig. 3, below, right ), and a gene expressionprofile of relative intensities can be produced.Those genes that predominate in sample one

are shown in red, those that predominate insample two are shown in green. Those genesthat have an equal gene expression in bothsamples are shown in yellow. The data fromeach comparison can be viewed as a histogramto determine those genes that have increasedor decreased in expression.

The histogram shown in Figure 4, above , isrepresentative of two normal skin samples.Note that more than 99 percent of the genesare expressed within a three-fold difference inexpression, showing a gaussian distribution of gene expression in normal skin from person toperson. The histogram in Figure 4, below , illus-trates a normal skin sample compared with thesame person s injured skin at 30 minutes. Ap-proximately 2 percent of genes (124 of 4000)in the wounded skin are increased greater than

two-fold, and less than 1 percent are increasedmore than three-fold (22 of 4000). There waslittle downregulation of gene expression at 30minutes.

Step 4

To analyze the data further, we used clusteranalysis to group genes based on expressionpatterns over the different time points (Fig. 5). We then tabulated those genes that were most upregulated during acute injury (30 minutes to4 hours; Table I) or chronic injury (1 month;

Table II). Those genes most upregulated im-mediately after injury are involved in transcrip-tion, signaling, and inflammation. This is ex-pected, because the initial cellular responseafter coagulation is inflammation. 28 Genes ex-pressed in the chronic wound show a different expression profile. Structural genes such asintracellular keratins in the epithelium andextracellular collagen types are most upregu-lated, consistent with the process of epithelial-ization. We are thus able to create an expressionprofile of those genes upregulated and down-

regulated during the wound healing process. A myriad of further analysis is possible with thisdata set. We could temporally follow the expres-sion changes in a subset of genes such as growthfactors, collagens, or inflammatory mediators. 35

In summary, we were able to identify 210 of 4000 genes examined (5 percent) that changed in expression in response to injury onthe basis of the few time points we examined. If we consider that there are 60,000 to 80,000genes in the human genome, we could extrap-olate that wound healing may potentially in- volve up to 4000 genes. Obviously, this is a



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guess and demonstrates the need for large-scale studies over longer periods of time todefine accurately how a wound heals at themRNA level.

These studies are underway by both investi-gators and pharmaceutical companies. Al-though arduous, these are powerful studiesthat are bound to raise new questions. By knowing which genes are expressed duringnormal wound healing, we could, in the future,identify and categorize nonhealing wounds ordetermine the effect of radiation and steroidson the normal wound healing expression re-sponse. In the future, a simple biopsy of anonhealing wound may be sent to the lab foranalysis to help direct treatment just as we now send off a urine sample for culture to guideour antibiotic choices.

CLINICAL IMPACT

At first glance, the sequencing of the humangenome may not seem to be of value to the

clinical plastic surgeon. After all, we will not beperforming cDNA expression profiling in theoffice in the foreseeable future. However, theinformation from the Human Genome Project has already impacted plastic surgeons. Patients who are BRCA1 and BRCA2 mutation carriersare being counseled for prophylactic bilateralmastectomies 29,30; some then opt for immedi-ate breast reconstruction. 31

The most promising results of the HumanGenome Project and its offspring technologies,such as microarrays, will be in the future as webetter understand biological processes at themost basic level. For example, gene expressionanalyses will aid in understanding the develop-ment process: for example, which sets of genesare coordinately regulated to achieve normaldevelopment of the craniofacial skeleton andlimbs. This has obvious implications in deter-mining the cause and perhaps the potentialtreatment of certain developmental anomalies.Some syndromes that are difficult to diagnose

FIG. 4 . (Above ) Histogram shows a comparison of the gene expression profile from two normal skin samples. More than 99percent of the genes fall within a three-fold change in expression, demonstrating the limited variability of gene expression innormal skin from one person to the next. ( Below ) Histogram shows a comparison of the gene expression profile of normal skincompared with the same patient s skin 30 minutes after injury. Note the increased gene expression (red shift to the right) inthe acutely wounded skin compared with the quiescent state.



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early in the neonatal period are likely to beaided by mRNA expression analysis or DNA mutational analysis provided by microarrays,thus enabling rapid, accurate, and early diag-

nosis. Obviously, the human genome researcheffort also raises important yet unanswered eth-ical, legal, and social questions.

TABLE I

Genes Expressed 30 Minutes after Injury

GeneIncrease

(fold) Function

Suppressor of cytokine signaling 20 Signaling3,4 Inositol phosphate signaling 12 SignalingRegulator of G protein signaling 6 SignalingTranscription factor 3 5 TranscriptionCCAAT box-binding transcript 1 7 TranscriptionElongation factor 1 10 TranscriptionMacrophage-stimulating 1 9 InflammationTNF receptor-1 6 InflammationTNF 5 InflammationMetallothionein 1L 4 Inflammation

TNF, tumor necrosis factor.

TABLE IIGenes Expressed 1 Month after Injury

GeneIncrease

(%) Function

Keratin 37 StructuralKeratin 5 18 StructuralCollage type I ( 2) 33 StructuralCollagen type III ( 1) 27 Structural Actin ( 2) 27 StructuralRegulator of G-protein signaling 1 6 SignalingMHC class II t ransact ivator 10 Inf lammationMHC class I1 7 InflammationMatrix metalloproteinase 21 5 Inf lammationLatent TGF- binding protein 1 5 Growth factor

MHC, major histocompatability complex; TGF, transforming growth fac-tor.

FIG. 5. Graphic representation of cluster analysis demonstrated for one patient. Because of size restraints, only 800 of the4000 genes are represented in black on the left. This column represents baseline gene expression in healthy unwounded skin(Nl). Genes that are upregulated at different time points are shown in green, and genes that are downregulated are shown inred. In this subset of 800 genes, at 30 minutes, the majority of the represented genes are upregulated (green). In comparison,at the 60 minute time point, there is a general downregulation of these same genes (red). A subset of these genes is listed inthe text box at right . Note that the cluster analysis groups genes with similar expression patterns; this is not based on the most variable genes. The most variable genes are listed in Tables I and II.



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The use of cDNA microarrays is likely tofoster a new level of understanding and cate-gorization of cancers, which may impact ourtreatment of melanoma. Future investigation islikely to prove that expression profiling is abetter prognosticator than Breslow depth 32 andthat expression profiling of excised melanomasmay even prove pivotal for performing or not performing sentinel lymph node biopsy. 11,33 As

better biological markers of invasive or aggres-sive melanoma are identified, plastic surgeonsmay have to change not only the current treat-ment algorithms but also reconstruction algo-rithms. For example, if genetic markers of lo-cally aggressive melanoma can be identified by microarrays, than those patients may be betterserved by skin grafting the defect to detect recurrences earlier.

The tool is already being used a great deal by pharmaceutical companies to understand theglobal impact a drug has on cells and tissues.Microarrays are being used to determine the

response of bacteria to certain antibiotics. 34Microarrays are also proving worthwhile tomonitor toxicity of various chemicals anddrugs to cells. 35,36 The expression profile of apatient may be a very useful way to study theresponse to certain drugs. 37 With time, phar-maceutical companies will design drugs that enhance or inhibit a specific molecule orgroups of molecules that were initially identi-fied by microarrays.

The Human Genome Project has providedenormous information about the basic set of inherited instructions for the development and functioning of a human being and is pro-foundly changing our understanding of celland tissue function. The identification of which genes are involved in specific biologicalprocesses will lead to a better understanding of

disease. In the near future, genomic technolo-gies will improve our diagnostic abilities, provide new opportunities for screening and pre- vention, and impact the treatment we provideto our patients. Once their strengths and lim-itations become better defined, microarraysand the other products of the Human GenomeProject are likely to find a vital role in thepractice of medicine and plastic surgery. TableIII provides a list of useful Web sites for furtherinformation.

Jana Cole, M.D.

Division of Plastic Surgery University of Washington Medical Center Box 356410 1959 N.E. Pacific Street Seattle, Wash. 98195 [email protected]

REFERENCES

1. Watson, J. D., and Crick, F. H. Molecular structure of nucleic acids:A structure fordeoxyribosenucleic acid.Nature 248: 765, 1974.

2. Venter, J. C., Adams, M. D., Myers, E. W., et al. Thesequence of the human genome. Science 291: 1304,

2001.3. Cole, J., Tsou, R., Wallace, K., Gibran, N., and Isik, F.Comparison of normal human skin gene expressionusing cDNA microarrays. Wound Repair Regen. 9: 77,2001.

4. Cole, J., Tsou, R., Wallace, K., Gibran, N. S., andIsik, F. F.The early gene expression profile of human skin toinjury using high-density cDNA microarrays. Wound Repair Regen. 9: 360, 2001.

5. Tsou, R., Cole, J. K., Nathens, A. B., et al. Analysis of hypertrophic and normal scar gene expression withcDNA microarrays. J. Burn Care Rehabil. 21: 541, 2000.

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TABLE IIIList of Useful Web Sites

Introductory WebsitesNational Center for Biotechnology Information:

http://www3.ncbi.nlm.nih.gov/ Weizmann Institute Bioinformatics unit:

http://bioinformatics.weizmann.ac.il//National Center for Genome resources:

http://www.ncgr.org/SWISS PROT: http://www.expasy.ch/sprot/Genes and diseases: http://www.ncbi.nlm.nih.gov/disease/

Genome databasesGenome channel: http://compbio.ornl.gov/channel/Entrez genome:

http://www3.ncbi.nlm.nih.gov/entrez/query.fcgi?db Genome Whitehead institute/MIT center for genome research:

http://www-genome.wi.mit.edu/Nucleotide and sequence databases

Genbank:http://www.ncbi.nlm.nih.gov/Genbank/index.html

DbEST: http://www.ncbi.nlm.nih.gov/dbEST/Unigene:

http://www.ncbi.nlm.nih.gov/UniGene/index.htmlNucleotide and protein sequence analysis

BLAST: http://www.ncbi.nlm.nih.gov/BLASTPROSITE: http://www.expasy.ch/prosite/

Expression data and analysisThe Brown Laboratory:

http://cmgm.stanford.edu/pbrown/Stanford Genome Center:

http://genome-www.stanford.edu/The Microarray Project at NHGRI:

http://www.nhgri.nih.gov/DIR/LCG/15K/HTML Whitehead/MIT Center for Genome Research:

http://waldo.wi.mit.edu/MPR/Proteomics

Danish Center for Human Genome Research:http://biobase.dk/cgi-bin/celis

EXPASY: http://www.expasy.ch/



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Human Genome n PRS 2002