VITELLOGENESIS AND THE REGULATION OF VITELLOGENIN GENE EXPRESSION IN THE SCALLOP.

(1)卵黄蛋白形成和卵黄素生成部位的激素调控扇贝卵巢卵母细胞发育过程中卵黄蛋白和总核糖核酸含量的增加以及雌二醇17-β(E_2)和脑及足神经节提取物对卵黄蛋白形成的促进作用体内外实验表明，卵巢应是卵黄蛋白原和E_2的产生部位，也是卵黄素的一个耐热、抗胰凝乳素和小于10,000分子量的因子促进卵黄的发生。仅在幼龄卵母细胞中发现雌激素受体(ER)样免疫反应的发现，提示了扇贝卵黄发生中的自动合成系统，以及CPG在ER诱导的基础上促进E_2诱导的卵黄发生的可能性。CSYP-1，登录号AB055960)是从扇贝卵巢c DNA文库中分离到的一个…Northern印迹分析表明，含有起始密码子和实际卵黄蛋白原基因的全长为12-13kb。氨基酸序列的同源性和分子进化树分析有力地支持了该序列为卵黄蛋白原基因的cDNA。卵黄蛋白原基因的表达在卵母细胞的生长过程中逐渐增强，但在产卵季节仍保持不变，此时卵巢充满了许多成熟的卵母细胞。与卵黄发生非常不同的是，CPG联合体外培养对卵母细胞的卵黄蛋白原基因表达水平没有影响。根据这些结果，初步的结论是：内源雌激素通过ER自动合成诱导卵母细胞中的卵黄蛋白原，并且卵黄蛋白原被修饰并积累到卵母细胞中。CPG中的一种促进E_2诱导的卵黄发生的因子同时增强了卵黄蛋白原基因的转录和翻译。成熟的卵母细胞终止卵黄蛋白原mRNA的翻译，这似乎是很长的半衰期。较少

(1) Hormonal regulation of yolk protein formation and producing site of vitellogeninThe increase in yolk protein and total RNA contents in the scallop ovary during oocyte growth and the promoting effect of estradiol-17β(E_2) and cerebral and pedal ganglion (CPG) extract on yolk protein formation in in vivo and in vitro experiment indicated that ovary should be a producing site of vitellogenin and E_2 and a factor in CPG which is heat stable, trypsin and chymotrypsin resist and less than 10,000 of molecular weight promotively regulate vitellogenesis. The founding of estrogen receptor (ER) like immuno-reactivity only in the young oocytes suggested the autosynthetic system in the scallop vitellogenesis and the possibility of the E_2-induced vitellogenesis promoted by CPG based on the ER induction.(2) Cloning of vitellogenin cDNA and regulation of vitellogenin gene expression.Cloned vitellogenin cDNA (clone No. cSYP-1, Accession No. AB055960) from cDNA library of scallop ovary was an incom … More plete length (1698 bp) with initiation codon and a actual vitellogenin mRNA was found to be 12-13 kb according to northern blot analysis. A homology and molecular phylogenic tree analysis of the amino acid sequence deduced from cDNA sequence strongly supported that the sequence was vitellogenin cDNA.The expression of vitellogenin mRNA increased during oocyte growth, but still kept the same level at spawning season when the ovary was full of many full grown oocyte. In vitro culture associated with CPG showed no influence on vitellogenin mRNA level, very unlike vitellogenesis.From these results, the following tentative conclusion is proposed Endogenous estrogen induces vitellogenin in the oocyte via ER autosynthetically and vitellogenin is modified and accumulated into the oocyte. A factor from CPG which promotes the E_2-induced vitellogenesis enhances the vitellogenin gene transcription and the translation at the same time. Full grown oocyte terminate translation of vitellogenin mRNA which appeared to be long half-life. Less