Delta-Notch signaling is involved in the segregation of the three germ layers in Xenopus laevis

摘要

Invertebrates,theinductionofthethreegermlayers(ectoderm,mesodermandendoderm)hasbeenextensivelystudied,butlessisknownabouthowtheysegregate.Here,weinvestigatedwhetherDelta-Notchsignalingisinvolvedinthisprocess.ActivatingthepathwayinthemarginalzonewithNotchsupICD/supresultedinanexpansionofendodermalandneuralectodermprecursors,leavingathinnermesodermalringaroundtheblastoporeatgastrulastage,whengermlayersaresegregated.Ontheotherhand,whenthepathwaywasblockedwithDelta-1supSTU/suporwithanantisensemorpholinooligonucleotideagainstNotch,thepan-mesodermalembrachyury(bra)/emdomainwasexpandedandtheneuralborderwasmovedanimalwards.Strikingly,thesuprablastoporalendodermwaseitherexpandedwhenDelta-1signalingwasblocked,orreducedafterthegeneralknock-downofNotch.Inaddition,eitheractivatingorblockingthepathwaydelaystheblastoporeclosure.WeconcludethattheprocessofdelimitingthethreegermlayersrequiresNotchsignaling,whichmaybefinelyregulatedbyligandsand/orinvolvenon-canonicalcomponentsofthepathway.Moreover,Notchactivitymustbemodulatedatappropriatelevelsduringthisprocessinordertokeepnormalmorphogeneticmovementsduringgastrulation./p/div