Actomyosin machinery endows cells with contractility at a single-cell level. However, within a monolayer, cells can be contractile or extensile based on the direction of pushing or pulling forces exerted by their neighbours or on the substrate. It has been shown that a monolayer of fibroblasts behaves as a contractile system while epithelial or neural progentior monolayers behave as an extensile system. Through a combination of cell culture experiments and in silico modelling, we reveal the mechanism behind this switch in extensile to contractile as the weakening of intercellular contacts. This switch promotes the build-up of tension at the cell–substrate interface through an increase in actin stress fibres and traction forces. This is accompanied by mechanotransductive changes in vinculin and YAP activation. We further show that contractile and extensile differences in cell activity sort cells in mixtures, uncovering a generic mechanism for pattern formation during cell competition, and morphogenesis.

肌动球蛋白机制赋予细胞单细胞水平的收缩性。然而，在单层内，细胞可以根据其相邻细胞或基质上施加的推力或拉力的方向而收缩或伸展。已经表明，单层成纤维细胞表现为收缩系统，而上皮或神经祖细胞单层表现为伸展系统。通过细胞培养实验和计算机模拟的结合，我们揭示了细胞间接触减弱导致的从伸展到收缩的转变背后的机制。这种开关通过肌动蛋白应力纤维和牵引力的增加促进细胞-基质界面张力的积累。这伴随着纽蛋白和 YAP 激活的机械传导变化。我们进一步表明，细胞活性的收缩和伸展差异对混合物中的细胞进行分类，揭示了细胞竞争和形态发生过程中模式形成的通用机制。