Neuritic guidance by nonneuronal cells of ganglionic origin☆

[摘要] Ciliaryganglia(CG)from8-day-oldchickembryoswereculturedasexplantsonahighlyadhesivecollagensubstratuminthepresenceoftheciliaryneuronotrophicfactor(CNTF).Aremarkablecorrelationwasfoundbetweentheformationofanoutgrowthofganglionicnonneuronalcellsandthetimingandextentofneuriticdevelopmentoutsidetheganglion.Neuriteswerenotseentoemergefromtheganglionbeforetheonset(24hrafterexplantation)ofanonneuronalcelloutgrowth.Afternonneuronsbegantomigrateoverthecollagensubstratum,neuritescouldbeseentoextendupto,butnotbeyondthedistallimitofthenonneuronaloutgrowth.Time-lapseanalysisshowedthatneuriticgrowthconescouldmoveinsynchronywithanonneuronwithwhichtheywereincontactaswellasoverthenonneuronalcellsurface,butnotonthecollagenlocateddistallytotheexternaledgeofthenonneuronaloutgrowth.FreshlydissectedCGswerealsogrownassecondaryexplantsonpreformedhostmonolayersofganglionicnonneurons.Thesesecondaryexplantsshowedconsiderableneuriticdevelopmentwithin24hr,whilecontrolgangliaexplantedoncollagenhadnotproducedneurites.Autoradiographicexperimentsindicatedthatthisneuriticoutgrowthoccurredonnonneuronalcellsemergingprecociouslyfromthesecondaryexplant,ratherthanonthepreexistinghostnonneurons.Electronmicroscopyof24-hrexplantsdemonstratedthat,insidetheganglion,neuriteswerealsoverycloselyassociatedwiththesurfaceofnonneuronalcells.Neuriticbehaviorinthisnonneuron/collagenterrainiscomparedwithpreviouslydescribedobservationsofCGexplantsonpolyornithine(PORN)ordissociatedCGneuronsonPORNorcollagen.TheseobservationsledtotheidentificationofaPORN-bindableneuritepromotingfactor(PNPF)whichdoesnotbindto,andisnotactiveon,collagen.ThehypothesisisdiscussedthatPNPFmoleculesarepresentonthesurfaceofnonneuronalcellsandthatthecellsowetothosemoleculestheircompetenceasasuitableterrainfortheelongationofneuriticprocesses.

[学科分类] 生物科学（综合）