Immunohistochemical Analysis of the Brachyury Protein in Wild-Type and Mutant Mouse Embryos

[摘要] ThemurineBrachyury(T)geneisrequiredinposteriormesodermformationandaxialdevelopment.MutantembryoslackingTgenefunctionaredeficientinnotochorddifferentiationandposteriormesodermformation,butmakeanteriormesoderm.PosterioraxialdevelopmentrequiresincreasingTactivityalongtherostrocaudalaxis.TheTgeneistransientlytranscribedinnascentandmigratingmesodermandcontinuouslyinthenotochord.ThemaintenanceofTexpressioninthenotochorddepends,directlyorindirectly,onwild-typeTactivity.InXenopusithasbeenshownthattheonsetofTexpressionoccursinresponsetomesoderm-inducinggrowthfactors.TheTproteinisbindingtoDNAandisprobablyinvolvedinthecontrolofgeneexpression.HereweshowthattheTproteinislocatedinthenucleus.WehaveanalyzedtheexpressionpatternofTproteininwild-typeandmutantembryosfromearlyprimitivestreakformationtotheendofthetailbudstage.ThroughoutallstagesofmesodermformationTproteinistransientlypresentinnascentandmigratingmesoderm.InthenotochordTproteinpersiststotheendofthetailbudstage.Itisalsotransientlydetectableintheforminggutendodermandinprospectiveneuroectodermoflaterembryos.ThisshowsthatTexpressionisnotstrictlycorrelatedwithacommitmentofcellstomesoderm.TheanalysisofthetaildevelopmentofT^Wis/+mutantembryosdemonstratedthattheformationoftheneuraltube,gut,andsomitesfromthetailbudproceedsintheabsenceofanotochord.Themaintenanceanddifferentiationofthesestructures,however,seemstodependonsignalsfromthenotochord.