Zhao Zihui, Li He, Yao Yisong, Zhao Yongfeng, Serra Francesca, Kawaguchi Kyogo, Zhang Hepeng, Sano Masaki
School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China.
Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China.
Nat Commun. 2025 Mar 12;16(1):2452. doi: 10.1038/s41467-025-57783-w.
Monolayers of confluent elongated cells are frequently considered active nematics, featuring topological defects. In extensile systems, where cells extend further along their long axis, they can accumulate at defects and escape from defects. Nevertheless, collective dynamics surrounding integer defects remain insufficiently understood. We induce diverse + 1 topological defects (asters, spirals, and targets) within neural progenitor cell monolayers using microfabricated patterns. Remarkably, cells migrate toward the cores of all + 1 defects, challenging existing theories and conventional extensile/contractile dichotomy, which predicts escape from highly bent spirals and targets. By combining experiments and a continuum theory derived from a cell-level model, we identify previously overlooked nonlinear active forces driving this unexpected accumulation toward defect cores, providing a unified framework to explain cell behavior across defect types. Our findings establish + 1 defects as probes to uncover key nonlinear features of active nematics, offering a methodology to characterize and classify cell monolayers.
汇合伸长细胞的单层通常被认为是具有拓扑缺陷的活性向列相。在拉伸系统中，细胞沿其长轴进一步延伸，它们可以在缺陷处聚集并从缺陷处逃逸。然而，围绕整数缺陷的集体动力学仍未得到充分理解。我们使用微加工图案在神经祖细胞单层中诱导出各种 +1 拓扑缺陷（星状体、螺旋体和靶状体）。值得注意的是，细胞会向所有 +1 缺陷的核心迁移，这挑战了现有理论和传统的拉伸/收缩二分法，后者预测细胞会从高度弯曲的螺旋体和靶状体中逃逸。通过结合实验和从细胞水平模型推导出来的连续体理论，我们确定了以前被忽视的驱动这种意外向缺陷核心积累的非线性活性力，提供了一个统一的框架来解释跨缺陷类型的细胞行为。我们的发现将 +1 缺陷确立为揭示活性向列相关键非线性特征的探针，提供了一种表征和分类细胞单层的方法。
