Direct Activation of a GATA6 Cardiac Enhancer by Nkx2.5: Evidence for a Reinforcing Regulatory Network of Nkx2.5 and GATA Transcription Factors in the Developing Heart ☆

摘要

ThezincfingertranscriptionfactorsGATA4,-5,and-6andthehomeodomainproteinNkx2.5areexpressedinthedevelopingheartandhavebeenshowntoactivateavarietyofcardiac-specificgenes.Tobegintodefinetheregulatoryrelationshipsbetweenthesecardiactranscriptionfactorsandtounderstandthemechanismsthatcontroltheirexpressionduringcardiogenesis,weanalyzedthemouseemGATA6/emgeneforregulatoryelementssufficienttodirectcardiacexpressionduringembryogenesis.Usingβ-galactosidasefusionconstructsintransgenicmice,a4.3-kb5prime;regulatoryregionthatdirectedtranscriptionspecificallyinthecardiaclineage,beginningatthecardiaccrescentstage,wasidentified.Thereafter,transgeneexpressionbecamecompartmentalizedtotheoutflowtract,aportionoftherightventricle,andalimitedregionofthecommonatrialchamberoftheembryonicheart.Furtherdissectionofthisregulatoryregionidentifieda1.8-kbcardiac-specificenhancerthatrecapitulatedtheexpressionpatternofthelargerregionwhenfusedtoaheterologouspromoterandasmaller500-bpsubregionthatretainedcardiacexpression,butwasquantitativelyweaker.TheemGATA6/emcardiacenhancercontainedabindingsiteforNkx2.5thatwasessentialforcardiac-specificexpressionintransgenicmice.ThesestudiesdemonstratethatemGATA6/emisadirecttargetgeneforNkx2.5inthedevelopingheartandrevealamutuallyreinforcingregulatorynetworkofNkx2.5andGATAtranscriptionfactorsduringcardiogenesis./p/div