Autonomous muscle cell differentiation in partial ascidian embryos according to the newly verified cell lineages☆

摘要

RecentanalysisofcelllineagesinascidianembryosbytheintracellularinjectionofatracerenzymehasclearlydemonstratedthatmusclecellsarederivednotonlyfromtheB4.1-cellpairoftheeight-cellstageembryo,ashashithertobeenbelieved,butalsofromboththeb4.2-andA4.1-cellpairs(H.NishidaandN.Satoh,1983,Dev.Biol.99,382a€“394).Inordertoreexaminethedevelopmentalautonomyinmusclelineagecells,theB4.1pairwasisolatedfromtheeight-cellstageembryo.TheprogenycellsoftheB4.1pair,aswellasthoseofthesixotherblastomeres,werethenallowedtodevelopinisolationintopartialembryos.AutonomousmusclecelldifferentiationnotonlyinpartialembryosoriginatingfromtheB4.1cellsbutalsointhosefromthesixotherblastomereswassubstantiatedby(a)occurrenceoflocalizedhistospecificmuscleacetylcholinesteraseand(b)developmentofmyofibrils.Theseresultssupportthevalidityoftherecentcelllineagestudyandconfirmedtheself-differentiationpotencyofmusclelineagecellsinascidianembryosaccordingtothenewlyverifiedcelllineages.