Analysis of Genes Expressed in.2 cell-stage.Mouse.Embryos.

我们的项目侧重于小鼠植入物的2细胞阶段。在小鼠胚胎发育中， zygotic基因在2细胞阶段被激活，以及与母体遗传产品的相互作用对于胚胎发育的进一步发展至关重要。如果要确定基因在2细胞阶段高度表达，我们有两种方法，一种方法是确定含有B1重复序列的cDNA，其中一种方法在早期胚胎中表达了基因。来自小鼠2细胞cDNA Iibrary，我们在100个独立克隆人中已经识别和表征。在这些cDNA中识别的B1序列的一般特征是：（i）在大多数情况下mRNA的非编码区域中存在的B1序列;（ii）B1序列的方向相对于转录的方向是完全随机的。在添加、表征这些cDNA克隆体以识别M31和M32的情况下，它们似乎在异色素修饰和tc-1中，它们也在成人测试中表达。采用了还原技术的另一种方法，我们已经识别了SSEC-D （特定阶段的胚胎克隆-D）基因，它们在2细胞阶段表达得很高。SSEC-D基因的特性及其产品揭示了：（一）它是一种新颖的基因，高度依赖于成熟和初级基因;（二）许多小鼠菌株有一个假基因;（三）它在每一个成人的tissues测试中被描述;（四）在大约15小时的帖子中被证实;它通常继承的产品将被延长约400 ntds，可能由多个A扩展。最后一个特征...... SSEC-D转录的阶段特定长度......是特别深入的，我们目前正在研究分子变化的更多细节，以确保根据这一特殊现象的发展计划。

Our project has focused on the 2-cell stage of mouse preimplantation embryo. In mouse embryogenesis, zygotic genes are activated around the 2-cell stage, and interaction of the zygotic gene products with maternally-inherited products are critical for further development of the embryo. In order to identify genes that are highly expressed at the 2-cell stage, we have taken two approaches.One approach was to identify cDNAs containing B1 repetitive sequences, which are over-represented in genes expressed in early embryos. From a mouse 2-cell cDNA Iibrary, we have identified and characterized around 100 independent clones. General characteristics of the B1 sequences identified in these cDNAs are that(i) the B1 sequences are present within non-coding regions of mRNA in most cases, (ii) the orientation of the B1 sequences relative to the orientation of transcripts are quite random. In addition, characterization of these cDNA clones led to identification of M31 and M32, which appear to be involved in heterochromatin modification, and tsec-1, which are also expressed in adult testis.The other approach employed the subtraction technique, and we have identified the SSEC-D (Stage-Specific Embryonic Clone-D) gene, which is highly expressed at the 2-cell stage. Characterization of the SSEC-D gene and its products has revealed that (i) it is a novel gene, highly conserved among rodent and primate, (ii) many mouse strains have one pseudo gene, (iii) it is expressed in every adult tissues tested, and (iv) at about 15 hours post fertilization, its maternally inherited products become elongated for about 400 ntds, probably by poly A extension. The last characteristics・・・stage-specific elongation of the SSEC-D transcripts・・・is particularly intriguing, and we are currently examining the molecular alterations more in details to understand the developmental program that causes this peculiar phenomenon.