Dynamic changes in mechanical microenvironments, such as cell crowding, regulate lineage fates as well as cell proliferation. Although regulatory mechanisms for contact inhibition of proliferation have been extensively studied, it remains unclear how cell crowding induces lineage specification. Here we found that a well-known oncogene, ETS variant transcription factor 4 (ETV4), serves as a molecular transducer that links mechanical microenvironments and gene expression. In a growing epithelium of human embryonic stem cells, cell crowding dynamics is translated into ETV4 expression, serving as a pre-pattern for future lineage fates. A switch-like ETV4 inactivation by cell crowding derepresses the potential for neuroectoderm differentiation in human embryonic stem cell epithelia. Mechanistically, cell crowding inactivates the integrin–actomyosin pathway and blocks the endocytosis of fibroblast growth factor receptors (FGFRs). The disrupted FGFR endocytosis induces a marked decrease in ETV4 protein stability through ERK inactivation. Mathematical modelling demonstrates that the dynamics of cell density in a growing human embryonic stem cell epithelium precisely determines the spatiotemporal ETV4 expression pattern and, consequently, the timing and geometry of lineage development. Our findings suggest that cell crowding dynamics in a stem cell epithelium drives spatiotemporal lineage specification using ETV4 as a key mechanical transducer.

机械微环境的动态变化（例如细胞拥挤）调节谱系命运以及细胞增殖。尽管接触抑制增殖的调节机制已被广泛研究，但仍不清楚细胞拥挤如何诱导谱系特异性。在这里，我们发现一种众所周知的癌基因，ETS 变体转录因子 4 (ETV4)，作为连接机械微环境和基因表达的分子传感器。在人类胚胎干细胞不断生长的上皮细胞中，细胞拥挤动态被转化为 ETV4 表达，作为未来谱系命运的预模式。细胞拥挤导致的类似开关的 ETV4 失活会抑制人胚胎干细胞上皮神经外胚层分化的潜力。从机制上讲，细胞拥挤使整合素-肌动球蛋白通路失活，并阻止成纤维细胞生长因子受体（FGFR）的内吞作用。 FGFR 内吞作用被破坏，通过 ERK 失活导致 ETV4 蛋白稳定性显着降低。数学模型表明，生长中的人类胚胎干细胞上皮细胞密度的动态精确地决定了 ETV4 的时空表达模式，从而决定了谱系发育的时间和几何形状。我们的研究结果表明，使用 ETV4 作为关键机械传感器，干细胞上皮中的细胞拥挤动力学驱动时空谱系规范。