Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
Philos Trans R Soc Lond B Biol Sci. 2020 Oct 12;375(1809):20190561. doi: 10.1098/rstb.2019.0561. Epub 2020 Aug 24.
Dynamic rearrangements of epithelial cells play central roles in shaping tissues and organs during development. There are also scenarios, however, in which epithelial cell movements synergize with the secretion of extracellular matrix to build rigid, acellular structures that persist long after the cells are gone. The formation of the micropyle provides an elegant example of this epithelial craftsmanship. The micropyle is a cone-shaped projection of the eggshell through which the sperm will enter to fertilize the oocyte. Though simple on the surface, both the inner structure and construction of the micropyle are remarkably complex. In this review, I first provide an overview of egg development, focusing on the key events required to understand micropyle formation. I then describe the structure of the micropyle, the cellular contributions to its morphogenesis and some interesting open questions about this process. There is a brief discussion of micropyle formation in other insects and fish to highlight the potential for comparative studies. Finally, I discuss how new studies of micropyle formation could reveal general mechanisms that epithelia use to build complex extracellular structures. This article is part of a discussion meeting issue 'Contemporary morphogenesis'.
上皮细胞的动态重排在发育过程中对组织和器官的形成起着核心作用。然而，也有一些情况是，上皮细胞的运动与细胞外基质的分泌协同作用，构建出坚硬的、无细胞的结构，这些结构在细胞消失后仍能长期存在。微孔的形成就是上皮细胞工艺的一个极好例子。微孔是卵壳的锥形突起，精子通过它进入卵母细胞受精。尽管表面上很简单，但微孔的内部结构和构造都非常复杂。在这篇综述中，我首先概述了卵子的发育，重点介绍了理解微孔形成所需的关键事件。然后，我描述了微孔的结构、对其形态发生的细胞贡献以及关于这个过程的一些有趣的开放性问题。简要讨论了其他昆虫和鱼类中的微孔形成，以突出比较研究的潜力。最后，我讨论了微孔形成的新研究如何揭示上皮细胞用于构建复杂细胞外结构的一般机制。本文是一次讨论会议的一部分，主题是“当代形态发生”。
