Muscle morphogenesis: Evidence for an organizing function of exogenous fibronectin☆

[摘要] Chickenmyoblastsandmyotubesattachto,andelongateupon,solidsubstratesonlyinthepresenceofexogenousfibronectinderivedfrom,forexample,serumorfibroblasts(M.Chiquet,E.C.Puri,andD.C.Turner,1979,J.Biol.Chem.254,5475–5482).Wehavesoughtanswerstotwoquestions:(1)whethermyoblastsdependonexogenousfibronectinforattachmentbecausetheythemselvessynthesizenoneortoolittleofthisglycoprotein;and(2)whetherinteractionofmyogeniccellswithfibroblast-derivedfibronectinmightguidemusclemorphogenesis.Underconditionsinwhichfibroblastssynthesizedfibronectinandreleaseditintothemedium,myoblastsandmyotubessynthesizedandaccumulatedonlysmallamountsoffibronectin.Althoughproliferatingmyogeniccellstreatedwith5-bromodeoxyuridineaccumulatefibronectinontheirsurfaces,otherevidencesuggeststhatnormalmyogenicprecursorcells,likemyoblastsandmyotubes,synthesizelittlefibronectin:(1)theaccumulationofnewlysynthesizedfibronectininuntreatedprimarymyogenicculturesisattributable,atleastinpart,tothefibroblastspresent;and(2)1-week-oldmyogenicclonesfailtoformafibronectinnetwork,incontrasttofibrogenicclonesofthesameageandcelldensity.Incryosectionsofchickembryos,lessfibronectinwasfoundinthepremusclemassesthaninthesurroundingmesenchyme.Thesplittingofthemuscleanlageninthelimbbudwascorrelatedwiththeappearanceoffibronectin-accumulatingcellsinthecleavagefurrows.Invitro,myoblastsdisplayedamarkedtendencytoalignthemselvesalongorientedfibrilsorstreaksofpurifiedfibronectinthathadbeendepositedonthesubstrate;thismyoblastalignmentinfluencedshapeandbranchingofthedevelopingmyotubes.Theseresultssuggestthatformationofmyotubesinacertainspatialarrangementduringmusclemorphogenesismayberegulatedbyafibronectin-containingmatrixproducedbyconnectivetissuecells.

[学科分类] 生物科学（综合）