Cell contact during early morphogenesis in the chick embryo☆

[摘要] Theprimitiveepitheliallayersofthechickblastoderm,theepiblastandhypoblast,areunderlainbydiscontinuousbasementlaminae.Primarymesenchymalcells,whichcomprisethemesoblastthatmigrateslaterallyfromtheprimitivestreak,makeclosejunctions(intercellularspace,25–100Ã…)andtightjunctions(noapparentextracellularspace)withthebasalsurfacesoftheepiblastandhypoblast.Closeandtightjunctionsarealsoprominentbetweenmesenchymalcells,especiallyalongtheirtrailingedges.Filopodiaaremostnumerousontheleadingedgesofthemigratingcellsaswouldbeexpectedifthecloseandtightjunctionsplayedaroleincontactinhibition,perhapsbymediatingelectricalcouplingbetweenthecells.Thetightjunctionswithinmesoblast,epiblast,andhypoblastareatfirstfocalinnature(maculaeoccludentes),butsubsequentlythosebetweencellsinthesametissuebecomemoreextensivewhilethosebetweencellsinunliketissuesaredisrupted.Whentheprimarymesenchymeorganizesitselfintoanepithelium(somite,lateral,andintermediatemesoderm),thetrailingendsofthecells,whichcontaintheGolgiorganelles,aredirectedtowardthemiddleofthemasswherezonulaeoccludentesappearnexttothenewlycreatedfreesurface.Subsequently,secondarymesenchymederivesfromthemesodermalepithelium.Themigratingcellsareconnectedbybroadtightjunctions(fasciaeoccludentes)whichseemtopersistasmaculaeoccludentesafterthepresumptiveconnectivetissuecellsdifferentiate.Withintheepithelia,maculaeadhaerentes(desmosomes)areparticularlywelldevelopedatlaterstagesandprobablycontributetotissue-specificintercellularadhesion.

[学科分类] 生物科学（综合）