Evidence for dosage compensation of an X-linked gene in the 6-day embryo of the mouse☆☆☆

[摘要] ThetimeatwhichdosagecompensationofanX-linkedgeneinthemouseisestablishedhasbeenestimatedbymeasuringtheactivitylevelsoftwoglycolyticenzymes,phosphoglyceratekinase(EC2.7.2.3)andtriosephosphateisomerase(EC5.3.1.1),duringearlydevelopmentofembryosfromXXandXOmice.DuringpreimplantationdevelopmentthelevelofphosphoglyceratekinaseinembryosfromXXmicewasconstantforthefirst48hrofdevelopment(2.55–2.71nmoles/hr/embryo)andthendroppedtoone-halftheearlierlevel(1.44nmoles/hr/embryo)by72hrofdevelopment.ThegeneraldevelopmentalprofileofphosphoglyceratekinasewassimilarinembryosfromXOmice;however,theabsolutelevelofenzymeactivitywasreducedtoapproximately1.4nmoles/hr/embryoduringthefirst48hrofdevelopmentandto0.9nmoles/hr/embryoby72hrofdevelopment.ThesedifferencesinphosphoglyceratekinaselevelsbetweenembryosfromXXandXOmicedisappearedbetweentheblastocystandeggcylinderstages(150hrpostplug)duringwhichtimetheactivitylevelshadincreasedto183and193nmoles/hr/eggcylinderforembryosfromXOandXXmice,respectively.TheactivitylevelfortriosephosphateisomeraseinembryosfromXXandXOmothersdidnotdifferatanystageofdevelopment;thissuggeststhatthegenecodingfortriosephosphateisomeraseisautosomal.Inadditionthelevelofactivityremainedconstantduringpreimplantationdevelopment(approximately3nmoles/hr/embryo)andthen,likephosphoglyceratekinase,increased100-foldbetweentheblastocystandeggcylinderstages.Thefrequencydistributionoftheactivityratio(triosephosphateisomerasetophosphoglyceratekinase)intheeggcylinderofindividualembryosfrombothXXandXOmotherswasdeterminedinordertodetectdifferencesamongXX,XOandXYembryos.Thesefrequencydistributionswereunimodal,andhencetheseresultscoupledwiththegenedosagedifferencesobservedduringpreimplantationdevelopmentindicatethatdosagecompensationforanX-linkedgenehasbeenestablishedinthe6-daymouseembryo.

[学科分类] 生物科学（综合）