Uemura T, Oda H, Kraut R, Hayashi S, Kotaoka Y, Takeichi M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Genes Dev. 1996 Mar 15;10(6):659-71. doi: 10.1101/gad.10.6.659.
Dynamic epithelial reorganization is essential for morphogenesis of various organs. In Drosophila embryos, for example the Malpighian tubule is generated by cellular rearrangement of a preexisting epithelium and the tracheal network is formed by outgrowth, branching, and fusion of epithelial vesicles. Here we report that the previously identified locus shotgun (shg) encodes DE-cadherin, an epithelial cell-cell adhesion molecule of the classic cadherin type and that zygotic shg mutations rather specifically impair processes of the dynamic epithelial morphogenesis. In the mutants, the Malpighian tubule disintegrated into small spherical structures, and the tracheal network formation was blocked in selected steps. The malformation of these organs could be rescued by overexpression of DE-cadherin cDNA under a heat shock promoter. Unexpectedly, the zygotic null condition did not severely affect general epithelial organization; most epithelial tissues maintained not only their cell-cell associations but also their apicobasal polarity in the mutants. The zygotic null mutant retained a certain level of maternally derived DE-cadherin molecules until the end of embryogenesis. These results suggest that zygotic DE-cadherin expression is critical for the rearrangement processes of epithelial cells, whereas the maternally derived DE-cadherin may serve only for the maintenance of the static architecture of the epithelia.
动态上皮细胞重排对于各种器官的形态发生至关重要。例如，在果蝇胚胎中，马氏管是由先前存在的上皮细胞的细胞重排产生的，而气管网络则是由上皮小泡的生长、分支和融合形成的。在此，我们报告先前鉴定的基因座shotgun（shg）编码DE-钙黏蛋白，一种经典钙黏蛋白类型的上皮细胞-细胞黏附分子，并且合子shg突变相当特异性地损害动态上皮形态发生过程。在突变体中，马氏管解体为小球形结构，并且气管网络形成在特定步骤中被阻断。这些器官的畸形可以通过在热休克启动子下过表达DE-钙黏蛋白cDNA来挽救。出乎意料的是，合子缺失状态并未严重影响一般上皮组织的组织；大多数上皮组织在突变体中不仅维持了它们的细胞-细胞连接，还维持了它们的顶-基极性。合子缺失突变体在胚胎发育结束前保留了一定水平的母源DE-钙黏蛋白分子。这些结果表明，合子DE-钙黏蛋白表达对于上皮细胞的重排过程至关重要，而母源DE-钙黏蛋白可能仅用于维持上皮的静态结构。
