Cote Lauren E, Feldman Jessica L
Department of Biology, Stanford University, Stanford, CA, United States.
Front Cell Dev Biol. 2022 Jun 21;10:887107. doi: 10.3389/fcell.2022.887107. eCollection 2022.
Epithelial tissues form continuous barriers to protect against external environments. Within these tissues, epithelial cells build environment-facing apical membranes, junction complexes that anchor neighbors together, and basolateral surfaces that face other cells. Critically, to form a continuous apical barrier, neighboring epithelial cells must align their apico-basolateral axes to create global polarity along the entire tissue. Here, we will review mechanisms of global tissue-level polarity establishment, with a focus on how neighboring epithelial cells of different origins align their apical surfaces. Epithelial cells with different developmental origins and/or that polarize at different times and places must align their respective apico-basolateral axes. Connecting different epithelial tissues into continuous sheets or tubes, termed epithelial fusion, has been most extensively studied in cases where neighboring cells initially dock at an apical-to-apical interface. However, epithelial cells can also meet basal-to-basal, posing several challenges for apical continuity. Pre-existing basement membrane between the tissues must be remodeled and/or removed, the cells involved in docking are specialized, and new cell-cell adhesions are formed. Each of these challenges can involve changes to apico-basolateral polarity of epithelial cells. This minireview highlights several examples of basal docking and how apico-basolateral polarity changes during epithelial fusion. Understanding the specific molecular mechanisms of basal docking is an area ripe for further exploration that will shed light on complex morphogenetic events that sculpt developing organisms and on the cellular mechanisms that can go awry during diseases involving the formation of cysts, fistulas, atresias, and metastases.
上皮组织形成连续的屏障以抵御外部环境。在这些组织中，上皮细胞构建面向环境的顶端膜、将相邻细胞锚定在一起的连接复合体以及面向其他细胞的基底外侧表面。至关重要的是，为了形成连续的顶端屏障，相邻的上皮细胞必须使其顶-基底外侧轴对齐，以在整个组织中建立整体极性。在这里，我们将综述整体组织水平极性建立的机制，重点关注不同来源的相邻上皮细胞如何使其顶端表面对齐。具有不同发育起源和/或在不同时间和地点极化的上皮细胞必须使其各自的顶-基底外侧轴对齐。将不同的上皮组织连接成连续的片层或管道，即上皮融合，在相邻细胞最初在顶端-顶端界面对接的情况下得到了最广泛的研究。然而，上皮细胞也可以基底-基底对接，这对顶端连续性提出了几个挑战。组织之间预先存在的基底膜必须进行重塑和/或去除，参与对接的细胞是特化的，并且会形成新的细胞-细胞粘附。这些挑战中的每一个都可能涉及上皮细胞顶-基底外侧极性的变化。这篇小型综述重点介绍了基底对接的几个例子以及上皮融合过程中顶-基底外侧极性如何变化。了解基底对接的具体分子机制是一个有待进一步探索的领域，这将有助于阐明塑造发育中生物体的复杂形态发生事件以及在涉及囊肿、瘘管、闭锁和转移形成的疾病过程中可能出现异常的细胞机制。
