The effects of calcium deficiency on the formation of the zonula occludens and blastocoel in the mouse embryo

[摘要] Themechanismoffluidtransportinthedevelopingpreimplantationmouseembryohasbeenstudiedinvitrobyinhibitingzonulartightjunctionformation.Compaction,themorphogeneticprocesspermittingzonularblastomereadhesionsatthe8-cellstage,wassuppressedbyloweringextracellularcalcium(Ca).TheCathresholdrequiredforcompactionis0.04–0.06mM,andinconcentrationsabovethethreshold,therateofcompactionisconcentrationdependent,whereastherateofblastocystformationisnotandproceedsnormally.At0.02mMCa,bothcompactionandblastocystdevelopmentarecompletelyprevented.Althoughfocaltightandgapjunctionsarepresent,zonulartightjunctionsdonotdevelop.WeconcludethatCaisrequiredforthemaximizationofcell-cellcontact,butnotforfocaltightjunctionandgapjunctionformation.Whenearlymorulaeareculturedin0.02mMCa,smalltrophoblasticvesiclesdevelopfrequentlywithintracellularfluidvacuoles.Ifearly8-cellembryosaresimilarlycultured,celldivisioncontinuesandmanyblastomeresacquiresmallintracellularmembrane-boundedvaculoes.Thesecoalesce,thecellvolumeincreases,andthenucleusbecomeseccentricallypositioned,resultinginagiantvacuolatedblastomerereminiscentofaminiaturizedblastocyst.Weproposethat(1)vacuoleformationmaybeanexaggerationofanintermediateintracellularstepinfluidtransportand(2)normalcellpolarityestablishedbyzonulartightjunctionsisrequiredfortranscellularfluidtransport.

[学科分类] 生物科学（综合）