Oda H, Tsukita S, Takeichi M
Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Kyoto Research Park, Kyoto, Chudoji Minami-machi, Shimogyo-ku, 600-8813, Japan.
Dev Biol. 1998 Nov 15;203(2):435-50. doi: 10.1006/dbio.1998.9047.
During Drosophila gastrulation, morphogenesis occurs as a series of cell shape changes and cell movements which probably involve adhesive interactions between cells. In the present study, we examined the dynamic aspects of cadherin-based cell-cell adhesion in the morphogenetic events to assess its contribution to morphogenesis. DE- and DN-cadherin show complementary expression patterns in the presumptive ectoderm and mesoderm at the mRNA level. We found that switching of cadherin expression from the DE- to the DN-type in the mesodermal germ layer occurred downstream of the mesoderm-determination genes twist and snail. However, examination of their protein expression patterns showed that considerable amounts of DE-cadherin remained on the surfaces of mesodermal cells during invagination, while DN-cadherin did not appear on the cell surfaces at this stage. Further immunocytochemical analysis of the localizations of DE-cadherin and its associated proteins Armadillo (beta-catenin) and Dalpha-catenin revealed dynamic changes in their distributions which were accompanied by changes in cell morphology in the neuroectoderm and mesoderm. Simultaneously, adherens junctions (AJs), based on the cadherin-catenin system, were shown to change their location, size, and morphology. These dynamic aspects of cadherin-based cell-cell adhesion appeared to be associated with the following: (1) initial establishment of the blastoderm epithelium, (2) acquisition of cell motility in the neuroectoderm, (3) cell sheet folding, and (4) epithelial to mesenchymal conversion of the mesoderm. These observations suggest that the behavior of the DE-cadherin-catenin adhesion system may be regulated in a stepwise manner during gastrulation to perform successive cell-morphology conversions. Moreover, the processes responsible for loss of epithelial cell polarity and elimination of preexisting DE-cadherin-based epithelial junctions during early mesodermal morphogenesis are discussed.
在果蝇原肠胚形成过程中，形态发生表现为一系列细胞形状变化和细胞运动，这可能涉及细胞间的黏附相互作用。在本研究中，我们检查了基于钙黏蛋白的细胞间黏附在形态发生事件中的动态方面，以评估其对形态发生的贡献。DE-钙黏蛋白和DN-钙黏蛋白在mRNA水平上在预定外胚层和中胚层中显示出互补的表达模式。我们发现，中胚层胚层中钙黏蛋白表达从DE型向DN型的转变发生在中胚层决定基因twist和snail的下游。然而，对它们蛋白质表达模式的检查表明，在中胚层细胞内陷过程中，相当数量的DE-钙黏蛋白仍保留在细胞表面，而DN-钙黏蛋白在这个阶段并未出现在细胞表面。对DE-钙黏蛋白及其相关蛋白犰狳（β-连环蛋白）和Dα-连环蛋白定位的进一步免疫细胞化学分析揭示了它们分布的动态变化，这些变化伴随着神经外胚层和中胚层细胞形态的变化。同时，基于钙黏蛋白-连环蛋白系统的黏着连接（AJs）显示出其位置、大小和形态的变化。基于钙黏蛋白的细胞间黏附的这些动态方面似乎与以下方面有关：（1）胚盘上皮的初始建立，（2）神经外胚层中细胞运动性的获得，（3）细胞片层折叠，以及（4）中胚层的上皮向间充质转化。这些观察结果表明，在原肠胚形成过程中，DE-钙黏蛋白-连环蛋白黏附系统的行为可能以逐步方式受到调节，以进行连续的细胞形态转化。此外，还讨论了早期中胚层形态发生过程中负责上皮细胞极性丧失和消除先前存在的基于DE-钙黏蛋白的上皮连接的过程。
