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Abstract：
As tissues grow and change shape during animal development, they physically pull and push on each other, and these mechanical interactions can be important for morphogenesis. During Drosophila gastrulation, mesoderm invagination temporally overlaps with the convergence and extension of the ectodermal germband; the latter is caused primarily by Myosin II-driven polarised cell intercalation. Here, we investigate the impact of mesoderm invagination on ectoderm extension, examining possible mechanical and mechanotransductive effects on Myosin II recruitment and polarised cell intercalation. We find that the germband ectoderm is deformed by the mesoderm pulling in the orthogonal direction to germband extension (GBE), showing mechanical coupling between these tissues. However, we do not find a significant change in Myosin II planar polarisation in response to mesoderm invagination, nor in the rate of junction shrinkage leading to neighbour exchange events. We conclude that the main cellular mechanism of axis extension, polarised cell intercalation, is robust to the mesoderm invagination pull. We find, however, that mesoderm invagination slows down the rate of anterior-posterior cell elongation that contributes to axis extension, counteracting the tension from the endoderm invagination, which pulls along the direction of GBE.
摘要：
随着动物发育过程中组织的生长和形状的变化，他们在身体上相互拉动和推动，这些机械相互作用对于形态发生可能很重要。在果蝇原肠胚形成期间，中胚层内陷与外胚层胚带的会聚和延伸在时间上重叠；后者主要是由肌球蛋白II驱动的极化细胞嵌入引起的。这里,我们研究了中胚层内陷对外胚层延伸的影响，检查对肌球蛋白II募集和极化细胞嵌入的可能的机械和机械转导作用。我们发现，胚带外胚层在与胚带延伸（GBE）正交的方向上被中胚层拉伸而变形，显示这些组织之间的机械耦合。然而,我们没有发现响应中胚层内陷的肌球蛋白II平面极化的显着变化，导致邻居交换事件的交界收缩率也是如此。我们得出结论，轴延伸的主要细胞机制，极化细胞嵌入，对中胚层内陷拉力具有鲁棒性。我们发现,然而,中胚层内陷减慢了促进轴延伸的前后细胞伸长的速度，抵消来自内胚层内陷的张力，它沿着GBE的方向拉。
