Bruce Ashley E E
Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
Dev Dyn. 2016 Mar;245(3):244-58. doi: 10.1002/dvdy.24353. Epub 2015 Oct 28.
Tissue thinning and spreading, a morphogenetic movement termed epiboly, is used widely during animal development. In zebrafish, epiboly is a prominent cell movement during gastrulation, whereby a squamous epithelium (the enveloping layer), a multi-layer of loosely packed cells (the deep cells), and a yolk nuclear syncytium (the yolk syncytial layer) undergo coordinated expansion to engulf the yolk and close the blastopore. Elucidating the mechanisms that underlie epiboly is important not only for understanding animal development in general, but also for providing insights into fundamental cell behaviors including cell intercalation, cell adhesion, cell signaling, and epithelial morphogenesis. Here, recent work is reviewed with a focus on findings that advance our understanding of (1) the role of actomyosin motors in the yolk cell to drive epiboly, (2) the mechanisms that underlie the spreading of the epithelial enveloping layer, and (3) the regulation of deep cell movements by E-cadherin based adhesion. A discussion of how these new insights add to the current view of epiboly and future prospects is also presented. Overall, the study of zebrafish epiboly can provide general and broadly applicable insights into the genetic, molecular, and cellular control of morphogenesis.
组织变薄与扩展，一种称为外包的形态发生运动，在动物发育过程中被广泛使用。在斑马鱼中，外包是原肠胚形成期间一种显著的细胞运动，在此过程中，单层扁平上皮（包被层）、多层松散排列的细胞（深层细胞）和卵黄核合胞体（卵黄合胞体层）会进行协调扩展以吞噬卵黄并关闭胚孔。阐明外包背后的机制不仅对于理解一般的动物发育很重要，而且对于深入了解包括细胞插入、细胞黏附、细胞信号传导和上皮形态发生在内的基本细胞行为也很重要。在此，我们综述了近期的研究工作，重点关注那些推动我们对以下方面理解的研究结果：（1）肌动球蛋白马达在卵黄细胞中驱动外包的作用；（2）上皮包被层扩展的潜在机制；（3）基于E-钙黏蛋白的黏附对深层细胞运动的调节。同时还讨论了这些新见解如何丰富了当前对外包的认识以及未来的研究前景。总体而言，对斑马鱼外包的研究能够为形态发生的遗传、分子和细胞控制提供普遍且广泛适用的见解。
