BMP Signaling Is Required for Heart Formation in Vertebrates

[摘要] Inthesestudies,wehavetakenadvantageofatransienttransgenicstrategyinXenopusembryostodemonstratethatBMPsignalingisrequiredinvivoforheartformationinvertebrates.EctopicexpressionofdominantnegativeTypeI(tALK3)orTypeII(tBMPRII)BMPreceptorsindevelopingXenopusembryosresultsinreductionorabsenceofheartformation.Additionally,blockingBMPsignalinginthismannerdownregulatesexpressionofXNkx2-5,ahomeoboxgenerequiredforcardiacspecification,priortodifferentiation.Notably,however,initialexpressionofXNkx2-5isnotaffected.Mutantphenotypescanberescuedbyco-injectionofmutantwithwild-typereceptorsorco-injectionofmutantreceptorswithXSmad1,adownstreammediatorofBMPsignaling.Whole-mountinsituanalysesindicatethatALK3andXSmad1arecoexpressedincardiogenicregions.Together,ourresultsdemonstratethatBMPsignalingisrequiredformaintenanceofXNkx2-5expressionandheartformationandsuggestthatALK3,BMPRII,andXSmad1maymediatethissignaling.