Development of Egg Fragments of the Ascidian Ciona savignyi: The Cytoplasmic Factors Responsible for Muscle Differentiation Are Separated into a Specific Fragment

[摘要] Theeggsofascidianscontaincytoplasmicdeterminantsresponsiblefordifferentiationoflarvalmusclecells.However,themolecularnatureandmodeofactionofmuscledeterminantsareunknownatpresent.Toestablishanappropriateexperimentalsystemforstudyingmuscledeterminants,wehavedevisedamethodforseparatingthedeterminantsintospecificeggfragments.ThetreatmentofunfertilizedeggsofCionasavignyiwithcytochalasinBfollowedbycentrifugationyielded(1)alarge,nucleatedredfragment,(2)asmall,enucleatedblackfragment,(3)asmall,enucleatedclearfragment,and(4)asmall,enucleatedbrownfragment.Wheninseminated,onlyredfragmentscleavedanddevelopedintoso-called"permanentblastulae,"inwhichthedifferentiationofepidermalcellswasevident.However,whenredfragmentswerefusedwithblackfragmentsandthefusionproductswereinseminated,thefusionproductsshowedaremarkableabilitytoexpressmuscle-specificmarkers.Inaddition,theabilityofblackfragmentstopromotetheexpressionofmuscle-specificmarkerswasevidentwhenthefragmentswerefusedwithpresumptive-epidermisblastomeres.Incontrast,clearandbrownfragmentsshowedlimitedabilitytopromotemuscledifferentiation.Theseresultssuggestthatthemuscledeterminantsarepresentinunfertilizedeggsandthatthedeterminantsareconcentratedintoblackfragmentsanddepletedfromredfragments.Thesetwofragmentsmayserveasanappropriateexperimentalsystemtodeterminethemolecularnatureofmuscledeterminantsinascidianeggs.

[学科分类] 生物科学（综合）