Choi Y S, Gumbiner B
Department of Pharmacology, University of California, San Francisco 94143.
J Cell Biol. 1989 Jun;108(6):2449-58. doi: 10.1083/jcb.108.6.2449.
The expression of the Ca2+-dependent epithelial cell adhesion molecule E-cadherin (also known as uvomorulin and L-CAM) in the early stages of embryonic development of Xenopus laevis was examined. E-Cadherin was identified in the Xenopus A6 epithelial cell line by antibody cross-reactivity and several biochemical characteristics. Four independent mAbs were generated against purified Xenopus E-cadherin. All four mAbs recognized the same polypeptides in A6 cells, adult epithelial tissues, and embryos. These mAbs inhibited the formation of cell contacts between A6 cells and stained the basolateral plasma membranes of A6 cells, hepatocytes, and alveolar epithelial cells. The time of E-cadherin expression in early Xenopus embryos was determined by immunoblotting. Unlike its expression in early mouse embryos, E-cadherin was not present in the eggs or early blastula of Xenopus laevis. These findings indicate that a different Ca2+-dependent cell adhesion molecule, perhaps another member of the cadherin gene family, is responsible for the Ca2+-dependent adhesion between cleavage stage Xenopus blastomeres. Detectable accumulation of E-cadherin started just before gastrulation at stage 9 1/2 and increased rapidly up to the end of gastrulation at stage 15. In stage 15 embryos, specific immunofluorescence staining of E-cadherin was discernible only in ectoderm, but not in mesoderm and endoderm. The ectoderm at this stage consists of two cell layers. The outer cell layer of ectoderm was stained intensely, and staining was localized to the basolateral plasma membrane of these cells. Lower levels of staining were observed in the inner cell layer of ectoderm. The coincidence of E-cadherin expression with the process of gastrulation and its restriction to the ectoderm indicate that it may play a role in the morphogenetic movements of gastrulation and resulting segregation of embryonic germ layers.
研究了非洲爪蟾胚胎发育早期阶段钙离子依赖的上皮细胞粘附分子E-钙粘蛋白（也称为卵粘蛋白和L-细胞粘附分子）的表达情况。通过抗体交叉反应和若干生化特性在非洲爪蟾A6上皮细胞系中鉴定出了E-钙粘蛋白。针对纯化的非洲爪蟾E-钙粘蛋白产生了四种独立的单克隆抗体。这四种单克隆抗体在A6细胞、成年上皮组织和胚胎中识别相同的多肽。这些单克隆抗体抑制A6细胞之间细胞接触的形成，并对A6细胞、肝细胞和肺泡上皮细胞的基底外侧质膜进行染色。通过免疫印迹法确定了非洲爪蟾早期胚胎中E-钙粘蛋白的表达时间。与在小鼠早期胚胎中的表达不同，E-钙粘蛋白在非洲爪蟾的卵或早期囊胚中不存在。这些发现表明，一种不同的钙离子依赖的细胞粘附分子，可能是钙粘蛋白基因家族的另一个成员，负责非洲爪蟾卵裂期卵裂球之间的钙离子依赖的粘附。E-钙粘蛋白在原肠胚形成开始前的第9.5阶段开始可检测到积累，并在第15阶段原肠胚形成结束时迅速增加。在第15阶段的胚胎中，E-钙粘蛋白的特异性免疫荧光染色仅在外胚层中可见，而在中胚层和内胚层中不可见。这个阶段的外胚层由两层细胞组成。外胚层的外层细胞染色强烈，染色定位于这些细胞的基底外侧质膜。在外胚层的内层细胞中观察到较低水平的染色。E-钙粘蛋白表达与原肠胚形成过程的一致性及其在外胚层中的局限性表明，它可能在原肠胚形成的形态发生运动以及由此导致的胚胎胚层分离中发挥作用。
