Auto/Cross-Regulation of Hoxb3 Expression in Posterior Hindbrain and Spinal Cord

[摘要] ThecomplexanddynamicpatternofHoxb3expressioninthedevelopinghindbrainandtheassociatedneuralcrestofmouseembryosiscontrolledbythreeseparatecis-regulatoryelements:elementI(regionA),elementIIIa,andther5enhancer(elementIVa).Wehaveexaminedthecis-regulatoryelementIIIabytransgenicandmutationalanalysistodeterminetheupstreamtrans-actingfactorsandmechanismsthatareinvolvedincontrollingtheexpressionofthemouseHoxb3geneintheanteriorspinalcordandhindbrainuptother5/r6boundary,aswellastheassociatedneuralcrestwhichmigratetothethirdandposteriorbranchialarchesandtothegut.Bydeletionanalysis,wehaveidentifiedthesequencerequirementswithina482-bpelementIII482.TwoHoxbindingsitesareidentifiedinelementIII482andwehaveshownthatinvitrobothHoxb3andHoxb4proteinscaninteractwiththeseHoxbindingsites,suggestingthatauto/cross-regulationisrequiredforestablishingtheexpressionofHoxb3intheneuraltubedomain.Interestingly,wehaveidentifiedanovelGCCAGGCsequencemotifwithinelementIII482,whichisalsorequiredtodirectgeneexpressiontoasubsetoftheexpressiondomainsexceptforrhombomere6andtheassociatedneuralcrestmigratingtothethirdandposteriorbranchialarches.ElementIII482candirectahigherlevelofreportergeneexpressioninr6,whichledustoinvestigatewhetherkreislerisinvolvedinregulatingHoxb3expressioninr6throughthiselement.However,ourtransgenicandmutationalanalysishasdemonstratedthat,althoughkreislerbindingsitesarepresent,theyarenotrequiredfortheestablishmentormaintenanceofreportergeneexpressioninr6.OurresultshaveprovidedevidencethattheexpressionofHoxb3intheneuraltubeuptother5/r6boundaryisauto/cross-regulatedbyHoxgenesandexpressionofHoxb3inr6doesnotrequirekreisler.

[学科分类] 生物科学（综合）

[关键词] Hoxb3;hindbrain;rhombomere;kreisler;neural crest;cis-regulation