10august2017|VOL548|NatuRE|219LEttERdoi:10.1038/nature23274ProlongedMek1/2suppressionimpairsthedevelopmentalpotentialofembryonicstemcellsJihoChoi1,2,3,4*,aaronJ.Huebner1,2,3,4*,KendellClement3,4,5,RyanM.Walsh1,2,3,4,andrejsavol1,KaixuanLin6,Hongcanggu5,BrunoDistefano1,2,3,4,JustinBrumbaugh1,2,3,4,sang-YongKim7,Jafarsharif8,ChristopherM.Rose9,armanMohammad5,JunkoOdajima2,JeanCharron10,toshishioda2,andreasgnirke5,stevengygi9,HaruhikoKoseki8,RuslanI.sadreyev1,andrewXiao6,alexanderMeissner3,4,5&KonradHochedlinger1,2,3,4ConcomitantactivationoftheWntpathwayandsuppressionofMapksignallingbytwosmallmoleculeinhibitors(2i)inthepresenceofleukaemiainhibitoryfactor(LIF)(hereaftertermed2i/L)inducesanaivestateinmouseembryonicstem(ES)cellsthatresemblestheinnercellmass(ICM)ofthepre-implantationembryo1.SincetheICMexistsonlytransientlyinvivo,itremainsunclearhowsustainedpropagationofnaiveEScellsinvitroaffectstheirstabilityandfunctionality.HereweshowthatprolongedcultureofmalemouseEScellsin2i/Lresultsinirreversibleepigeneticandgenomicchangesthatimpairtheirdevelopmentalpotential.Furthermore,wefindthatfemaleEScellsculturedinconventionalserumplusLIFmediumphenocopymaleEScellsculturedin2i/L.Mechanistically,wedemonstratethattheinhibitionofMek1/2ispredominantlyresponsiblefortheseeffects,inpartthroughthedownregulationofDNAmethyltransferasesandtheircofactors.Finally,weshowthatreplacementoftheMek1/2inhibitorwithaSrcinhibitorpreservestheepigeneticandgenomicintegrityaswellasthedevelopmentalpotentialofEScells.Takentogether,ourdatasuggestthat,althoughshort-termsuppressionofMek1/2inEScellshelpstomaintainanICM-likeepigeneticstate,prolongedsuppressionresultsinirreversiblechangesthatcompromisetheirdevelopmentalpotential.DysregulationofDNAmethylationaswellasofWntandMapksignallinghasbeenlinkedtocellulartransformationandchromosomalinstabilityinEScells2–5.Therefore,wesoughttodeterminewhethersustainedperturbationoftheWnt/MapkpathwayandassociatedDNAhypomethylationduring2i/Lcultureaffectsthestabilityandfuncti...
