Many tissues are produced by specialized progenitor cells emanating from epithelia via epithelial-to-mesenchymal transition (EMT). Most studies have so far focused on EMT involving single or isolated groups of cells. Here we describe an EMT-like process that requires tissue-level coordination. This EMT-like process occurs along a continuous front in the Drosophila optic lobe neuroepithelium to produce neural stem cells (NSCs). We find that emerging NSCs remain epithelial and apically constrict before dividing asymmetrically to produce neurons. Apical constriction is associated with contractile myosin pulses and involves RhoGEF3 and down-regulation of the Crumbs complex by the E3 ubiquitin ligase Neuralized. Anisotropy in Crumbs complex levels also results in accumulation of junctional myosin. Disrupting the regulation of Crumbs by Neuralized lowered junctional myosin and led to imprecision in the integration of emerging NSCs into the front. Thus, Neuralized promotes smooth progression of the differentiation front by coupling epithelium remodeling at the tissue level with NSC fate acquisition.

中文翻译：

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果蝇视叶上皮向神经干细胞转变的组织范围协调需要神经化

许多组织是由上皮细胞通过上皮间质转化 (EMT) 产生的特化祖细胞产生的。迄今为止，大多数研究都集中在涉及单个或孤立的细胞群的 EMT 上。在这里，我们描述了一个类似于 EMT 的过程，需要组织层面的协调。这种类似 EMT 的过程沿着果蝇视叶神经上皮的连续前沿发生，产生神经干细胞 (NSC)。我们发现，新兴的神经干细胞在不对称分裂产生神经元之前仍然是上皮细胞，顶部收缩。顶端收缩与收缩性肌球蛋白脉冲相关，并涉及 RhoGEF3 和 E3 泛素连接酶 Neuralized 对 Crumbs 复合物的下调。面包屑复合物水平的各向异性也会导致连接肌球蛋白的积累。神经化扰乱了 Crumbs 的调节，降低了连接肌球蛋白，并导致新兴 NSC 整合到前沿的不精确性。因此，Neuralized 通过将组织水平上皮重塑与 NSC 命运获取相结合，促进分化前沿的平稳进展。