Conserved co-regulation and promoter sharing of hoxb3a and hoxb4a in zebrafish

摘要

Theexpressionofzebrafishemhoxb3a/emandemhoxb4a/emhasbeenfoundtobemediatedthroughfivetranscripts,emhoxb3a/emtranscriptsIndash;IIIandemhoxb4a/emtranscriptsIndash;II,drivenbyfourpromoters.Alsquo;masterrsquo;promoter,locatedabout2nbsp;kbdownstreamofemhoxb5a/em,controlstranscriptionofapre-mRNAcomprisingexonsequencesofbothgenes.Thisuniquegenestructureisproposedtoprovideanovelmechanismtoensureoverlapping,tissue-specificexpressionofbothgenesintheposteriorhindbrainandspinalcord.Transgenicapproacheswereusedtoanalyzethefunctionsofzebrafishemhoxb3a/em/emhoxb4a/empromotersandenhancersequencescontainingregionsofhomologythatwerepreviouslyidentifiedbycomparativegenomics.Twoneuralenhancerswereshowntoestablishspecificanteriorexpressionborderswithinthehindbrainandmediateexpressionindefinedneuronalpopulationsderivedfromhindbrainrhombomeres(r)5to8,suggestingalateroleofthegenesinneuronalcelllineagespecification.Speciescomparisonshowedthatthezebrafishemhoxb3a/emr5andr6enhancercorrespondedtoasequencewithinthemouseHoxAclustercontrollingactivityofemHoxa3/eminr5andr6,whereasahomologousregionwithintheHoxBclusteractivatedemHoxb3/emexpressionbutlimitedtor5.Weconcludethatthesimilarityofemhoxb3a/em/emHoxa3/emregulatorymechanismsreflecttheshareddescentofbothgenesfromasingleancestralparaloggroup3gene./p/div