ANALYSIS AND CLONING OF THE MOUSE EXED GENE

虽然胎盘发育或功能障碍是 人类妊娠期胚胎死亡的最常见原因 和其他脊椎动物，很少有人知道的遗传调控， 胚外发育一个职能单位确定在 7号染色体上的白化缺失复合体，这在 小鼠的早期着床后是胚外外胚层 开发区（exed）。缺失纯合子胚胎 切除这个区域显示胚胎外的异常 结构，特别是在胚外外胚层， 严重缩小和固缩。这些胚胎的发育 它们在胚胎7.5-8.0天左右死亡。尚不清楚 是否主要影响胚外发育， 胚胎外胚层也很小。exed的角色将是 通过拯救胚胎外部分或胚胎部分来澄清 四倍体-二倍体嵌合体的表型。删除 互补分析表明，20 kb的缺失 区域对于表型是必要的。但目前还不清楚 该区域是否足以在缺失时引起表型， 或者是否在20 kb区域外去除的其它基因也 有助于exed表型。为了澄清这个问题， 将使用具有靶向的Cre-loxP系统删除区域 同源重组最后，exed将被位置克隆， 搜索在20 kb区域中开始。

Although failure of placental development or function is one of the most common causes of embryonic death during gestation in humans and other vertebrates, little is known about the genetic regulation of extraembryonic development. One functional unit identified in the albino-deletion complex on chromosome 7 which is important during early postimplantation in the mouse is the extraembryonic ectoderm development (exed) region. Embryos homozygous for deletions removing this region display abnormalities of extraembryonic structures, particularly in the extraembryonic ectoderm which is severely reduced and pyknotic. Development of these embryos is truncated and they die around embryonic day 7.5-8.0. It is unknown whether the primary effect is on extraembryonic development since the embryonic ectoderm is also small. The role of exed will be clarified by rescuing either the extraembryonic or embryonic portion of the phenotype with tetraploid-diploid chimeras. Deletion complementation analyses have demonstrated that loss of a 20 kb regiori is necessary for the phenotype. However it is not known whether this region is sufficient to cause the phenotype when deleted, or whether other genes removed outside the 20 kb region also contribute to the exed phenotype. To clarify this issue, the 20 kb region will be deleted using the Cre-loxP system with targeted homologous recombination. Finally, exed will be positionally cloned, with the search beginning in the 20 kb region.