Cytogenetic analysis of oocytes and early preimplantation embryos from XO mice☆

[摘要] ThemeioticsegregationpatternoftheXchromosomeinXOmicewasdeterminedbycountingsecondmeioticmetaphasechromosomes.Atotalof584oocyteswascollectedfromsuperovulatedbutunmatedXOandXXmice.Secondmeioticmetaphase(MII)countsindicatedthattheXchromosomeinXOmicedidnotsegregaterandomlybutremainedpreferentiallyintheoocyte.Increasedmaternalagehadnoeffectuponthissegregationpattern.SelectionagainstXOandYOpreimplantationembryoswasevaluatedbyobservingtheirrelativefrequenciesduringfirstandsecondcleavagedivisions.Acombinedtotalof1650preimplantationeggswascollectedfromsuperovulatedandmatedXOandXXfemalemice.Eggswereobtainedduringmetaphaseoffirst(CI)orsecondcleavage(CII)divisionsbyinjectingmatedfemaleswithcolchicineat28or49hr,respectively,afterhumanchorionicgonadotrophin(HCG)administration.Priortoanalysis,chromosomeswerebandedbytrypsin-Giemsa,whichfacilitatedspecificchromosomeidentification,includingtheXandY.TheproportionofXX,XY,XO,andYOembryosobservedatCIfromXOfemaleswasnotsignificantlydifferentfromexpectedvaluesbasedonMIIcounts.AtCII,asignificantdifferencewasobservedfromtheexpectedproportionofembryoclassesresultingfromareductioninXOandYOembryos.Theresultsprovidecytogeneticevidenceemphasizingthat,inorderfordevelopmenttocontinue,atleastonefunctionalXchromosomeisnecessaryasearlyasthetwo-cellstage.Triploidone-andtwo-cellembryoswereobservedmorefrequentlyinembryosfromXOthanXXfemales.Thesexratiowasnotsignificantlydifferentfrom1:1duringeithercleavagestageregardlessofthetypeoffemalefromwhichtheembryoswerederived.

[学科分类] 生物科学（综合）