MicroRNomics, a newly emerging approach for disease biology

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Review

MicroRNomics:anewlyemergingapproachfordiseasebiology

ChunxiangZhang

RNAandCardiovascularResearchLaboratory,DepartmentofAnesthesiology,NewJerseyMedicalSchool,University

ofMedicineandDentistryofNewJersey,Newark,NewJersey

Submitted7February2008;acceptedinfinalform21February2008

ZhangC.MicroRNomics:anewlyemergingapproachfordiseasebiology.

PhysiolGenomics33:139–147,2008.FirstpublishedFebruary26,2008;

doi:10.1152/physiolgenomics.00034.2008.—Genomicevidencerevealsthat

geneexpressioninhumansispreciselycontrolledincellular,tissue-type,

temporal,andcondition-specificmanners.Completelyunderstandingtheregu-

latorymechanismsofgeneexpressionisthereforeoneofthemostimportant

issuesingenomicmedicine.Surprisingly,recentanalysesofthehumanand

animalgenomeshavedemonstratedthatthemajorityofRNAtranscriptsare

relativelysmall,noncodingRNAs(sncRNAs),ratherthanlarge,proteincoding

messageRNAs(mRNAs).Moreover,thesesncRNAsmayrepresentanovel

importantlayerofregulationforgeneexpression.Themostimportantbreak-

throughinthisnewareaisthediscoveryofmicroRNAs(miRNAs).miRNAs

compriseanovelclassofendogenous,small,noncodingRNAsthatnegatively

regulategeneexpressionviadegradationortranslationalinhibitionoftheir

targetmRNAs.Asagroup,miRNAsmaydirectlyregulateϳ30%ofthegenes

inthehumangenome.InkeepingwiththenomenclatureofRNomics,whichis

tostudysncRNAsonthegenomicscale,“microRNomics”iscoinedhereto

describeanovelsubdisciplineofgenomicsthatstudiestheidentification,expres-

sion,biogenesis,structure,regulationofexpression,targets,andbiologicalfunc-

tionsofmiRNAsonthegenomicscale.Agrowingbodyofexcitingevidence

suggeststhatmiRNAsareimportantregulatorsofcelldifferentiation,proliferation/

growth,mobility,andapoptosis.ThesemiRNAsthereforeplayimportantrolesin

developmentandphysiology.Consequently,dysregulationofmiRNAfunctionmay

leadtohumandiseasessuchascancer,cardiovasculardisease,liverdisease,

immunedysfunction,andmetabolicdisorders.microRNomicsmaybeanewly

emergingapproachforhumandiseasebiology.

microRNAs;genomics;geneexpression;cancer;cardiovasculardisease

ITISCLEARTHATGENEEXPRESSIONinthehumanisprecisely

controlledinacell,tissue,time,andcondition-specificmanner.

Large-scalemicroarraydatasuggestthatdifferentcells,tissues,

andorgansystemswithinanorganism(includinghumans)

havedifferentgeneexpressionprofiles,althoughtheyhavethe

samegenome.Moreover,thesegeneexpressionsignaturesare

sensitivetochangesincondition,suchasdevelopment,dis-

eases,environmentchanges,andtherapeuticdrugs(10,36,75,

94).Therefore,completelyunderstandingtheregulatorymech-

anismsofgeneexpressionisoneofthemostimportantissues

ingenomicmedicine(36,59,75,97).Anyimportantbreak-

throughsinthisresearchareawillhavethepotentialtogive

risetoimpactsonmodernclinicalmedicineindiagnosisand

therapy,becausemostofhumandiseasesaremultigene(mul-

tifactor)diseases,inwhichtheexpressionofmultiplegenesis

changeddirectlyorindirectly(15,19,41,91).

SincethediscoveryoftheDNAdouble-helixstructureby

WatsonandCrick(120)in1953,thestandardpathwayofinformationflowinacellfromDNAtomessageRNA

(mRNA)toproteinhasbeenthedominantthemeinmolecular

biology.However,recentanalysesofthehumanandanimal

genomeshavedemonstratedthatthemajorityofRNAtran-

scriptsarenotproteincodingRNAs(mRNAs),butnoncoding

RNAs(ncRNAs)(77,105,108).Indeed,large-scalecomple-

mentaryDNAsequencingandgenometilingarraystudieshave

shownthatϳ50%ofgenomicDNAinhumansistranscribed

intoRNAtranscripts,ofwhich2%istranslatedintoproteins

andtheremaining98%isncRNAs(38,77,78,105,108).In

general,thesizesofthemajorityofncRNAspeciesvaryfrom

18ntto500nt,wellbelowthesizeofthemajorityofmRNA

species,andarethereforetermedsmallncRNAs(sncRNAs).

ThetermncRNAiscommonlyemployedforRNAthatdoes

notencodeaprotein,butthisdoesnotmeanthatsuchRNAsdo

notcontaininformationorhavefunction(38,77,78,105,108).

Forexample,ribosomalRNAsandtransferRNAs,whichmake

upalargeproportionofRNAbasedonamount,aretwoknown

sncRNAsthatprovidehelpforproteinexpression.Quitere-

cently,twonovelclassesofsncRNAswerediscovered:

microRNAs(miRNAs)andsmallinterferingRNAs(siRNAs)

(38,78,108).BothhavestrongregulatoryeffectsonmRNA

translationandrepresentanovelimportantlayerforgene

expression(38,78,108).AnalogoustothefirstRNA

revolu-Articlepublishedonlinebeforeprint.Seewebsitefordateofpublication

(http://physiolgenomics.physiology.org).

Addressforreprintrequestsandothercorrespondence:C.Zhang,RNAand

CardiovascularResearchLaboratory,Dept.ofAnesthesiology,NewJerseyMed-

icalSchool,Univ.ofMedicineandDentistryofNewJersey,185So.OrangeAve.,

MSB-E548,Newark,NJ07101-1709(e-mail:zhangc3@umdnj.edu).PhysiolGenomics33:139–147,2008.

FirstpublishedFebruary26,2008;doi:10.1152/physiolgenomics.00034.2008.

1094-8341/08$8.00Copyright©2008theAmericanPhysiologicalSociety139