genomic imprinting | genetics | Britannica

genomic imprinting, process wherein a gene is differentially expressed depending on whether it has been inherited from the mother or from the father. genomicimprinting Sections Article IntroductionImprintingmechanismsImprintingandfetaldevelopmentImprintingandcognitionandbehaviourafterbirth FastFacts RelatedContent AdditionalInfo MoreArticlesOnThisTopic AdditionalReading Contributors ArticleHistory Home Health&Medicine Genetics&Evolution genomicimprinting genetics Print print Print Pleaseselectwhichsectionsyouwouldliketoprint: TableOfContents Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/science/genomic-imprinting More GiveFeedback ExternalWebsites Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). FeedbackType Selectatype(Required) FactualCorrection Spelling/GrammarCorrection LinkCorrection AdditionalInformation Other YourFeedback SubmitFeedback Thankyouforyourfeedback Oureditorswillreviewwhatyou’vesubmittedanddeterminewhethertorevisethearticle. JoinBritannica'sPublishingPartnerProgramandourcommunityofexpertstogainaglobalaudienceforyourwork! ExternalWebsites AmericanSocietyofMammologists-GenomicImprintingasaMechanismofReproductiveIsolationinMammals NationalInstitutesofHealth-GeneticsHomeReference-WhatareGenomicImprintingandUniparentalDisomy? NationalCenterforBiotechnologyInformation-PubMedCentral-GenomicImprinting LearnGeneticsGeneticScienceLearningCenter-UniversityofUtahHealthSciences-GenomicImprinting ProceedingsofNationalAcademyofSciences-GenomicImprinting,Action,andInteractionofMaternalandFetalGenomes Academia-GenomicImprinting By OmarSultanHaque | ViewEditHistory RelatedTopics: gene allele hydatidiformmole geneticexpression imprintingdefect ...(Showmore) Seeallrelatedcontent→ genomicimprinting,processwhereinageneisdifferentiallyexpresseddependingonwhetherithasbeeninheritedfromthemotherorfromthefather.Such“parent-of-origin”effectsareknowntooccuronlyinsexuallyreproducingplacentalmammals.ImprintingisoneofanumberofpatternsofinheritancethatdonotobeythetraditionalMendelianrulesofinheritance,whichassumeindifferenceabouttheparentaloriginofanallele(analleleisanyoneoftwoormoregenesthatmayoccuralternativelyatagivensiteonachromosome).Traitsarethereforeabletobepasseddownmaternalorpaternallines. Imprintingmechanisms Imprintingcanoccurwhenoneofthegene’sparentalallelesissilencedthroughouttheembryonicdevelopmentoftheindividualbyanalterationinparentalDNAmadeduringparentalgametogenesis(theformationofgametes,orsperminmalesandeggsinfemales).Theotherparentalalleleisthereforeallowedexpressionduringembryonicdevelopment.AmechanismbywhichthisoccursisDNAmethylation(theadditionofaCH3,ormethyl,grouptospecificregionsofDNA)atimprintingcontrolregions(ICRs).IntracellularDNA-readingmechanismsexistafterfertilizationtocheckthatthecorrectparentalallelehasbeenalloweddifferentialexpression. Imprintingandfetaldevelopment Imprintinghasbeenabletoexplaincertainpredicamentsoflifeinutero.Anumberofimprintedgenesarerelatedtoembryonicandfetalgrowthandthustheextractionofresourcesfromtheuterineenvironmentforgrowth.Motherandfather,however,havedifferentinterestsinhowresourcesareextracted,becauseofasymmetricalparentalinvestmentineachgivenchild.Thisarisesfromthefactthatmotherscanonlyhaveonechildeveryninemonthsforapproximately20years,whereasafathercouldconceivablyimpregnatemanydifferentwomenfrompubertyuntildeath. Systematicknockout(inactivation)studiesofkeyimprintedgenes,especiallyasperformedonmice,haveprovidedsupportforthehypothesisthatimprintedgenesthatallowexpressionofpaternallyinheritedallelestendtodrivemoreextractionofnutrientsfromthemotherduringgestationandafterbirthtoproducealargerchild.Incontrast,imprintedgenesthatallowexpressionofmaternallyinheritedalleleswilltendtodrivemechanismstopreventthedisproportionateutilizationofresourcesbythefetus.AcommonlycitedexampleofthisdifferentialresourcetransferinmiceisthepaternallyexpressedgeneIgf2(insulin-likegrowthfactor2),whichenhancesfetalgrowthandplacentalnutrienttransportcapacity,andthematernallyexpressedIgf2receptor(Igf2r),whichdegradesexcessiveIgf2protein. Manyoftheeffectsofimprintedgenesoccurintheplacenta,acrucialsiteforresourceandnutrienttransfer.Forexample,anovergrownplacenta(hydatidiformmole)resultswhenmaternalimprintsaremissing.Additionally,inSilver-Russellsyndrome(orRussell-Silversyndrome),amaternaluniparentaldisomy(bothcopiesofachromosomeorpartialchromosomeareinheritedfromoneparent),growthrestrictionispresent.Similareffectsarefoundinothercasesofdisorderedimprinting.Preeclampsia,forexample,inwhichdisorderedimprintinghasbeenimplicated,alsodemonstratesgrowthrestrictioninutero.Manyofthesediseasescanbeunderstoodonlywithinthecontextofimprintingasacommonmechanismofparentalconflictandmanipulationofthephenotypicoutcomeofchildren. Imprintingandcognitionandbehaviourafterbirth Althoughonlyapproximately100humangenesareknowntobesubjecttoparent-of-origineffects,theseprovetohavetremendousimplicationsforthedevelopmentandeventualadultattributesofpeople,includingcognitiveandbehavioralattributes.Imprintingeffects,similartoothergeneticexpressionpatterns,maymanifestasearlierageofonseteffectsorchangesinseverity. InTurnersyndrome,whichaffectsfemalesandischaracterizedbythedeletionofoneXchromosome(femalesnormallycarrytwoXchromosomes),aparent-of-origineffectmayinfluencesocialandintellectualfunctioning.TheaffectedfemalecouldhavereceivedheronlyXchromosomefromherfather(Xp)orhermother(Xm).StudieshavesuggestedthatneurodevelopmentinXpTurnersyndromepatientsissimilartothatofhealthyfemales,whereasneurodevelopmentinXmpatientsisaltered.Otherstudies,however,haveyieldedconflictingresults. OmarSultanHaque