Loss of Dnmt1 catalytic activity reveals multiple roles for DNA methylation during pancreas development and regeneration

摘要

Developmentalmechanismsregulatinggeneexpressionandthestableacquisitionofcellfatedirectcytodifferentiationduringorganogenesis.Moreover,itislikelythatsuchmechanismscouldbeexploitedtorepairorregeneratedamagedorgans.DNAmethyltransferases(Dnmts)areenzymescriticalforepigeneticregulation,andareusedinconcertwithhistonemethylationandacetylationtoregulategeneexpressionandmaintaingenomicintegrityandchromosomestructure.Wecarriedouttwoforwardgeneticscreensforregulatorsofendodermalorgandevelopment.Inthefirst,wescreenedforalteredmorphologyofdevelopingdigestiveorgans,whileinthesecondwescreedforthelackofterminallydifferentiatedcelltypesinthepancreasandliver.Fromthesescreens,weidentifiedtwomutantallelesofzebrafishemdnmt1/em.Bothlesionsarepredictedtoeliminateemdnmt1/emfunction;oneisamissensemutationinthecatalyticdomainandtheotherisanonsensemutationthateliminatesthecatalyticdomain.Inzebrafishemdnmt1/emmutants,thepancreasandliverformnormally,butbegintodegenerateafter84nbsp;hpostfertilization(hpf).Acinarcellsarenearlyabolishedthroughapoptosisby100nbsp;hpf,thoughneitherDNAreplication,norentryintomitosisishaltedintheabsenceofdetectableDnmt1.However,endocrinecellsandductsarelargelyspared.Surprisingly,emdnmt1/emmutantsandemdnmt1/emmorpholino-injectedlarvaeshowincreasedcapacityforpancreaticbetacellregenerationinaninduciblemodelofpancreaticbetacellablation.Thus,ourdatasuggestthatDnmt1isdispensableforpancreaticductorendocrinecellformation,butnotforacinarcellsurvival.Inaddition,Dnmt1mayinfluencethedifferentiationofpancreaticbetacellprogenitorsorthereprogrammingofcellstowardthepancreaticbetacellfate./p/div