Center for Biological Systems Analysis, Albert-Ludwigs-University Freiburg, Habsburgerstrasse 49, 79104 Freiburg, Germany.
Faculty of Biology, Ludwig-Maximilians-University Munich, Grosshaderner Str. 2-4, 82152 Planegg-Martinsried, Germany.
Development. 2019 Sep 6;146(17):dev171256. doi: 10.1242/dev.171256.
How actomyosin generates forces at epithelial adherens junctions has been extensively studied. However, less is known about how a balance between internal and external forces establishes epithelial cell, tissue and organ shape. We used the egg chamber to investigate how contractility at adherens junctions in the follicle epithelium is modulated to accommodate and resist forces arising from the growing germ line. We found that between stages 6 and 9, adherens junction tension in the post-mitotic epithelium decreases, suggesting that the junctional network relaxes to accommodate germline growth. At that time, a prominent medial Myosin II network coupled to corrugating adherens junctions develops. Local enrichment of medial Myosin II in main body follicle cells resists germline-derived forces, thus constraining apical areas and, consequently, cuboidal cell shapes at stage 9. At the tissue and organ level, local reinforcement of medial junction architecture ensures the timely contact of main body cells with the expanding oocyte and imposes circumferential constraints on the germ line guiding egg elongation. Our study provides insight into how adherens junction tension promotes cell and tissue shape transitions while integrating the growth and shape of an internally enclosed structure .
肌动球蛋白在细胞连接黏附处产生力的机制已得到广泛研究。然而，对于细胞、组织和器官的形状如何通过内外力的平衡来建立，人们知之甚少。我们利用卵室来研究滤泡上皮细胞黏附连接处的收缩能力是如何被调节以适应和抵抗由不断生长的生殖细胞系产生的力的。我们发现，在阶段 6 到 9 之间，有丝分裂后上皮细胞的黏附连接张力降低，这表明连接网络会松弛以适应生殖细胞的生长。此时，一个与波纹状黏附连接连接的明显的中部肌球蛋白 II 网络发育。在主体滤泡细胞中中部肌球蛋白 II 的局部富集抵抗生殖细胞产生的力，从而限制了顶端区域，进而在第 9 阶段限制了立方体形细胞的形状。在组织和器官水平上，中部连接结构的局部强化确保了主体细胞与不断扩展的卵母细胞的及时接触，并对指导卵伸长的生殖细胞施加了圆周约束。我们的研究深入了解了黏附连接张力如何促进细胞和组织形状的转变，同时整合了内部封闭结构的生长和形状。
