The preimplantation mammalian embryo: Characterization of intercellular junctions and their appearance during development☆

[摘要] Junctionsindevelopingmammalianembryoswereinvestigatedwithlanthanumtracerandfreeze-fracturemethods.Theoutermostblastomeresofmousemorulaepossessfocaltightjunctionswhichbecomezonularandexcludelanthanum,therebyseparatingthe“inner”cellsfromthematernalenvironment.Thiscompartmentalization,creatingamicroenvironmentinsidetheembryo,mayberequiredforcelldeterminationandfortheaccumulationoffluidduringblastocoelexpansion.Desmosomesappearforthefirsttimeattheblastocyststageinthetrophoblastjunctionalcomplexwhichalsoischaracterizedbygapjunctionsandazonulaoccludenswithunderlyingmicrofilament-likematerialandmicrotubules.Bothgapandtightjunctionshavebeenvisualizedinfreeze-fracturereplicasofrabbitblastocysts.Thezonulaoccludensformsapermeabilitybarrierwhichisconsistentwiththehightranstrophoblastelectricalresistance.Mousepresumptiveandmatureinnercellmass(ICM)cellswereassociatedbyfrequentgapjunctionswhereasjunctionalcomplexeswereabsent.TrophoblastgapandadheringjunctionsandcytoplasmicprocessesappearedtofixtheICMtoonepoleoftheembryoandpartiallyisolateitfromtheblastocoel.ThesefindingssupporttheideathattheICMandtrophoblastcommunicateuponimplantationandrequirethattheintercellularjunctionsbetweenthembedissemblediftheICMistomigratetoamesometrialposition.

[学科分类] 生物科学（综合）