Muscle development in Ciona intestinalis requires the b-HLH myogenic regulatory factor gene Ci-MRF

摘要

Theactivityofmyogenicregulatoryfactor(MRF)genesisessentialforvertebratemuscledevelopment,whereasinvertebratemuscledevelopmentislargelyindependentofMRFfunction.Thisdifferenceindicatesthatmyogenesisiscontrolledbydistinctregulatorymechanismsinthesetwogroupsofanimals.HereweusedoverexpressionandgeneknockdowntoinvestigatetheroleinembryonicmyogenesisofthesingleMRFgeneoftheinvertebratechordateemCionaintestinalis/em(emCi-MRF/em).InjectionofemCi-MRF/emmRNAintoeggsresultedinincreasedembryonicmuscle-specificgeneactivityandrevealedthemyogenicactivityofemCi-MRF/embyinducingtheexpressionoffourmusclemarkergenes,emAcetylcholinesterase/em,emActin/em,emTroponinI/em,andemMyosinLightChain/eminnon-musclelineages.Conversely,inhibitingemCi-MRF/emactivitywithantisensemorpholinosdown-regulatedtheexpressionofthesegenes.Consistentwiththeeffectsofmorpholinosonmusclegeneactivity,larvaeresultingfrommorpholinoinjectionwereparalyzedandtheirldquo;musclerdquo;cellslackedmyofibrils.WeconcludethatemCi-MRF/emisrequiredforlarvaltailmuscledevelopmentandthusthatanMRF-dependentmyogenicregulatorynetworkprobablyexistedintheancestoroftunicatesandvertebrates.ThispossibilityraisesthequestionofwhethertheearliestmyogenicregulatorynetworkswereMRF-dependentorMRF-independent./p/div