Patterning the Embryonic Heart: Identification of Five Mouse Iroquois Homeobox Genes in the Developing Heart

摘要

WeisolatedcDNAsofmouseemIroquois/em-relatedhomeoboxgenesemIrx1,-2,-3,-4,/emand-em5/emandcharacterizedtheirpatternsofexpressioninthedevelopingheart.emIrx1/emandemIrx2/emwerefoundtobeexpressedspecificallyintheventricularseptumfromtheonsetofitsformationonward.Infetalstages,theexpressionofbothgenesappearedtograduallybecomeconfinedtothemyocardiumoftheatrioventricularbundleandbundlebranchesoftheformingventricularconductionsystem.emIrx3/emwasfoundtobeexpressedspecificallyinthetrabeculatedmyocardiumoftheventricles.emIrx4/emexpressionwasobservedinasegmentofthelinearhearttubeandtheatrioventricularcanalandventricularmyocardiumincludingtheinnercurvatureafterlooping,resemblingthepatternofemMLC2V./emTranscriptsforemIrx5/emweredetectedspecificallyintheendocardiumliningtheventricularandatrialworkingmyocardiumthatalsoexpressedvonWillebrandfactor,butwereabsentfromtheendocardiumoftheendocardialcushions,i.e.,theatrioventricularcanal,innercurvature,andoutflowtract.ThespatiodevelopmentalpatternofemIrx5/emmatchedthatofemANF,/emamarkerfortheformingworkingmyocardiumofthechambers.Takentogether,allmembersoftheemIrx/emgenefamilywerefoundtobeexpressedinhighlyspecificpatternsinthedevelopingmouseheart,suggestingacriticalroleinthespecificationofthedistinctcomponentsofthefour-chamberedheart./p/div