Myosin synthesis in cultures of differentiating chicken embryo skeletal muscle☆

[摘要] Myosinsynthesisrateshavebeenmeasuredinculturesofdifferentiatingchickembryomusclecellsbefore,duringandfollowingaperiodofrapidcellfusionleadingtotheformationoffunctionalstriatedmuscle.Priortothisfusion“burst”thereisalowlevelofmyosinsynthesisattributabletoasmallnumberofmultinucleatedmyotubesnormallypresentinthecultureby24hr.Thislowlevelofsynthesisisnotaffectedbybromodeoxyuridineatconcentrationsknowntoblockmyogenesis.Myosinsynthesisbeginsatalinearlyincreasingratewithalagperiodofapproximately4hrfollowingthemainfusionburst.Cellfusionisreversiblyblockedbyadditionofethylene-glycol-bis(aminoethylether)N,N′-tetraaceticacid(EGTA)totheculturemedium.EGTAhasahighaffinityforcalciumionsandtheEGTA-fusionblockisreversedbyadditionofcalcium.EGTAdoesnotinterferewithmyosinsynthesisonceithasbeeninitiatedincontrolcultures.MyoblastswilldivideinthepresenceofEGTAatleastonce.By60hrinEGTAcultures,themyoblastshaveceaseddividingandarearrestedinG0orG1ofthecellcycle.Ontheadditionofcalcium,thesecellsfusewithanaveragerateof10%perhourandcompletethemainfusionburstwithin6hr.EGTA-fusion-blockedcellsdonotsynthesizemyosinuntilfusionispermittedbycalciumaddition.Thelagperiodformyosinsynthesisinthesereleasedcellsisapproximately4hrlongerthanforcontrolcultures.WhileEGTA-fusion-blockedcellscannotsynthesizemyosin,theyhavedifferentiatedtothepointofbeingcompetenttofuse.SuchcellswillfuseoncalciumadditioninthepresenceofactinomycinDorcycloheximide.Itistentativelyconcludedthat,intheregulationofchickenskeletalmusclemyogenesis,cellfusionpotentialandthepotentialformyosinsynthesisaredevelopednotsimultaneously,butsequentially.

[学科分类] 生物科学（综合）