Regulatory Analysis of the Mouse Hoxb3 Gene: Multiple Elements Work in Concert to Direct Temporal and Spatial Patterns of Expression

摘要

TheexpressionpatternofthemouseemHoxb3/emgeneisexceptionallycomplexanddynamiccomparedwiththatofothermembersoftheemHoxb/emcluster.TherearemultipletypesoftranscriptsforemHoxb3/emgene,andtheanteriorboundariesofitsexpressionvaryatdifferentstagesofdevelopment.TwoenhancersflankingemHoxb3/emonthe3prime;and5prime;sidesregulateemHoxb2/emandemHoxb4,/emrespectively,andthesecontrolregionsdefinethetwoendsofa28-kbintervalinandaroundtheemHoxb3/emlocus.ToassaytheregulatorypotentialofDNAfragmentsinthisintervalwehaveusedtransgenicanalysiswithaemlacZ/emreportergenetolocateemcis/em-elementsfordirectingthedynamicpatternsofemHoxb3/emexpression.Ourdetailedanalysishasidentifiedfournewandwidelyspacedemcis/em-actingregulatoryregionsthatcantogetheraccountformajoraspectsoftheemHoxb3/emexpressionpattern.ElementsIb,IIIa,andIVbcontrolgeneexpressioninneuralandmesodermaltissues;elementVacontrolsmesoderm-specificgeneexpression.ThemostanteriorneuralexpressiondomainofemHoxb3/emiscontrolledbyanr5enhancer(elementIVa);elementIIIadirectsreporterexpressionintheanteriorspinalcordandhindbrainuptor6,andtheregionAenhancer(inelementI)mediatesposteriorneuralexpression.Hence,theregulationofsegmentalexpressionofemHoxb3/eminthehindbrainisdifferentfromthatofemHoxa3,/emastwoseparateenhancerelementscontributetoexpressioninr5andr6.Themesoderm-specificelement(Va)directsreporterexpressiontoprevertebraC1at12.5dpc,whichistheanteriorlimitofparaxialmesodermexpressionforemHoxb3./emWhentestedincombinations,theseemcis/em-elementsappeartoworkasmodulesinanadditivemannertorecapitulatethemajorendogenousexpressionpatternsofemHoxb3/emduringembryogenesis.Togetherourstudyshowsthatmultiplecontrolelementsdirectreportergeneexpressionindiversetissue-,temporal-,andspatiallyrestrictedsubsetoftheendogenousemHoxb3/emexpressiondomainsandworkinconcerttocontroltheneuralandmesodermalpatternsofexpression./p/div