Cardiac Troponin I Is a Heart-Specific Marker in the Xenopus Embryo: Expression during Abnormal Heart Morphogenesis

[摘要] CardiactroponinI(troponinIc)expressionisrestrictedtotheheartatallstagesofXenopusdevelopment.Whole-mountinsituhybridizationandNorthernblotanalysisindicatesthattroponinIcisfirstexpressedintailbudembryos(stage28)aboutthetimeofthefirstcytologicalheartdifferentiationandabout24hrbeforebeatingtissueisobserved.Wehaveusedthismarkertoexamineabnormalheartmorphogenesisinembryostreatedwithretinoicacidandlithium.Whenretinoicacidisadministeredtoembryospriortoheartspecification,hearttissueisreducedandoftencompletelyablated.Whenembryosaretreatedafterheartspecification,butbeforetheheartprimordiummigratestotheventralmidline,themigrationisunaffectedbutsmaller,abnormalheartsresult.Lithiumtreatmentofcleavagestageembryoscausesanincreaseinhearttissue.Inseverelydorsalizedembryos,hearttissuecanbefoundaroundtheentireembryowiththeexceptionofasmallgapatthemostdorsalpoint.Thisgapindicatesthatmigrationofthehearttotheventralmidlinedoesnotoccurintheseembryos.Laterindevelopment,acentrallylocated,beatingheartisobservedindorsalizedembryos.Thetimingofitsappearancesuggeststhatitisformedbymovementsnormallyassociatedwithheartmorphogenesisratherthanmigration.