Somitogenesis, the primary segmentation of the vertebrate embryo, is associated with oscillating genes that interact with a wave of cell differentiation. The necessity of cell-matrix adherence and embryonic tension, however, suggests that mechanical cues are also involved. To explicitly investigate this, we applied surplus axial strain to live chick embryos. Despite substantial deformations, the embryos developed normally and somite formation rate was unaffected. Surprisingly, however, we observed slow cellular reorganizations of the most elongated somites into two or more well-shaped daughter somites. In what appeared to be a regular process of boundary formation, somites divided and fibronectin was deposited in between. Cell counts and morphology indicated that cells from the somitocoel underwent mesenchymal-epithelial transition; this was supported by a Cellular Potts model of somite division. Thus, although somitogenesis appeared to be extremely robust, we observed new boundary formation in existing somites and conclude that mechanical strain can be morphologically instructive.

脊椎动物胚胎的主要分裂，即体发生与与细胞分化浪潮相互作用的振荡基因有关。然而，细胞基质依附性和胚胎张力的必要性表明，机械线索也参与其中。为了明确地对此进行研究，我们将多余的轴向应变应用于活的鸡胚。尽管有很大的变形，但胚胎发育正常，而体节的形成率不受影响。然而，令人惊讶的是，我们观察到了最伸长的节节缓慢地重组为两个或更多形状良好的子节节。在似乎是边界形成的规则过程中，体节分裂并且纤连蛋白沉积在其间。细胞计数和形态学表明，来自体细胞的细胞经历了间充质-上皮转化。这由Somite部门的Cellular Potts模型支持。因此，尽管体细胞生成似乎非常健壮，但我们观察到现有体中新的边界形成，并得出结论，机械应变在形态上具有指导意义。