Synthesis of secretory proteins in developing mouse yolk sac☆

[摘要] Synthesisofsecretoryproteinsinthedevelopingmousevisceralyolksacwasstudied.Newlysynthesizedproteinswerelabeledwith[35S]methionineandcharacterizedbytwo-dimensionalgelelectrophoresis.AlargeincreaseintherelativerateofsynthesisofasmallnumberofproteinsoccurredbetweenDays9.5and15.5ofdevelopment.Theseproteinswerethepredominantproteinssynthesizedandsecretedbytheyolksacthroughoutthisperiodofgestation.Twooftheseproteinswereidentifiedasα-fetoproteinandtransferrinbyspecificimmunoprecipitation.α-Fetoproteinsynthesisincreasedfromabout3%ofthetotalproteinsynthesisatDay9.5toabout26%atDay15.5afterwhichitdeclinedslightly.Therelativerateoftransferrinsynthesishadasimilardevelopmentalpattern,reachingthehighestlevel(5%)atDay15.5,butdeclinedmorerapidlythanα-fetoproteinsynthesis.Quantitatively,thesetwoproteinsrepresentedabout60%ofthetotalsecretedprotein.Gestationalchangesinthecontentofα-fetoproteinmessengerRNAweredeterminedbyhybridizationanalysisusingα-fetoproteincomplementaryDNAprobe.Thepercentageofα-fetoproteinmessengerRNAintotalyolksacRNAincreasedaboutninefoldfromDay9.5toDay14.5.Thisincreasecorrelatedwellwiththeincreaseintherelativerateofα-fetoproteinsynthesisduringtheidenticalperiod.ThisstudysuggeststhatafterDay9.5theyolksaciscompletingadifferentiationprocesswhichischaracterizedbythepreferentialexpressionofasmallgroupofsecretoryproteingenes.

[学科分类] 生物科学（综合）