Yolk sac: Site of developmental microheterogeneity of mouse α-fetoprotein☆

[摘要] α-Fetoproteinwasobservedtobesynthesizedinmousefetalliverandyolksacbyincorporationofradioactiveleucineintoappropriatetissuecultures.Culturedfetalliverduringearly(Day13.5)andlate(Day16.5)developmentsecretedpredominantlythemaximallysialylatedFp5.Incontrast,theyolksacsecretedadevelopmentallychangingarrayofα-fetoprotein:Day11.5yolksacsecretedpredominantlytheunsialylatedFp1,atDay13.5,theyolksacsecretedallfiveelectrophoreticformsofα-fetoprotein,andbyDay16.5,onlyFp5waspredominantlysecreted,asinthefetalliver.Toascertainwhetherthe3H-labeledproteinsthatappearedintheregionsofα-fetoproteinonpolyacrylamidegelsrepresentedα-fetoprotein,immunoprecipitationswithanti-α-fetoproteinwerecarriedout.Aftertheimmunoprecipitations,radioactivityintheregionsofmarkerα-fetoproteinonpolyacrylamidegelswasdecreasedtobackgroundlevels.Whensodiumdodecylsulfate-polyacrylamidegelelectrophoresisoftheimmunoprecipitateswasperformed,radioactivitypeakscomigratedwithmarkerα-fetoprotein.Theundersialylatedα-fetoproteinformsdonotappeartoarisebylossofsialicacidfollowingsecretionasdeterminedbymixingexperimentsofyolksacandfetalliverinculture.Thecontributionofα-fetoproteinsynthesizedandsecretedbyfetalliverandyolksacatDays13.5and16.5ofdevelopmentwascompared.Day13.5yolksacincorporated6.7timesasmuchradioactivityintosecretedα-fetoproteinasdidfetalliveratthistime.Theseresultssuggestthatduringearlydevelopment,theyolksacisprimarilyresponsibleforthesynthesisandsecretionoftheundersialylatedformsofα-fetoprotein.Inadditiontothemicroheterogeneityofα-fetoproteinattributedtothenumberofsialicacidresiduesattachedtotheglycoprotein,thereappearedtobeotherchangesinα-fetoprotein:Fp5synthesizedfromfetallivermigratedslightlyfasteronpolyacrylamidegelsthanthatfromyolksac.

[学科分类] 生物科学（综合）