Binding of Germ Cells to Mutant SId Sertoli Cells Is Defective and Is Rescued by Expression of the Transmembrane Form of the c-kit Ligand

摘要

Mutationsinthesteel(Sl)locus,encodingthec-kitligand(KL),areassociatedwithimpairedgermcelldevelopmentinmice.TwoformsofKLexist:onemoresteadilyassociatedwiththeplasmamembraneandonemoreeasilyreleasedasasolubleprotein.WereportherethattheexpressionofthetwomRNAscodingforthetwodifferentformofKLisdevelopmentallyregulatedinmousetestis.AtbirththetwomRNAsareexpressedatanequalratio.Startingafter6daysoflife,andinparalleltoinitiationofgermcelldifferentiation,themRNAencodingthemembrane-associatedformofKLbecomesmoreabundant.Germcells,andespeciallyspermatogonia,expressc-kit;thusmembrane-boundKLcouldmediateadhesionbetweenSertolicellsandgermcells.Wefind,infact,thatSertolicellsfromSl/Sldmutantmice,whichdonotexpressthemRNAforthemembrane-associatedformofKL,areunabletobindgermcells.Introductionofaplasmidexpressingthetransmembraneform,butnotthesolubleform,ofKLrestorestheabilityofSertolicellsfromSl/Sldmutantmicetobindgermcells.Thesedatasuggestthatpreferentialexpressionofthemembrane-anchoredformofKLinSertolicellsmayhavearoleinmediatingadhesionofc-kit-expressinggermcellstoSertolicells.