Mitotic cell rounding accelerates epithelial invagination

摘要

Mitotic cells assume a spherical shape by increasing their surface tension and osmotic pressure by extensively reorganizing their interphase actin cytoskeleton into a cortical meshwork and their microtubules into the mitotic spindle. Mitotic entry is known to interfere with tissue morphogenetic events that require cell-shape changes controlled by the interphase cytoskeleton, such as apical constriction. However, here we show that mitosis plays an active role in the epithelial invagination of the Drosophila melanogaster tracheal placode. Invagination begins with a slow phase under the control of epidermal growth factor receptor (EGFR) signalling; in this process, the central apically constricted cells, which are surrounded by intercalating cells, form a shallow pit. This slow phase is followed by a fast phase, in which the pit is rapidly depressed, accompanied by mitotic entry, which leads to the inter-nalization of all the cells in the placode. We found that mitotic cell rounding, but not cell division, of the central cells in the placode is required to accelerate invagination, in conjunction with EGFR-induced myosin II contractility in the surrounding cells. We propose that mitotic cell rounding causes the epithelium to buckle under pressure and acts as a switch for morphogenetic transition at the appropriate time.%早期胚胎中的关键形态形成步骤之一是基板rn(上皮层中的板状结构,它们产生继而形成复rn杂器官的三维结构)的内陷.在这项研究中,rnTakefumi Kondo和Shigeo Hayashi提出了驱动rn果蝇气管基板细胞的上皮内陷的一个新颖机rn制.他们发现,基板的中央细胞的有丝分裂细rn胞变圆(但不是分裂)是加快内陷所必需的,与rn周围细胞中由上皮生长因子受体诱导的肌球蛋rn白-II的收缩相一致.他们提出,细胞变圆造成rn上皮在压力下弯曲变形,并加快内陷.