Integer topological defects provide a new way to quantify and classify cell sheets
Zhao, Z.; Li, H.; Yao, Y.; Zhao, Y.; Serra, F.; Kawaguchi, K.; Zhang, H.; Chate, H.; Sano, M.
Show abstract
Sheets of confluent cells are often considered as active nematics, with accumulation at [Formula] topological defects and escape from [Formula] defects being widely recognized. However, collective dynamics surrounding integer-charge defects remain poorly understood, despite its biological importance. By using microfabricated patterns, we induce diverse +1 topological defects (aster, spirals, and target) within monolayers of neural progenitor cells. Remarkably, cells are consistently attracted to the core of +1 defects regardless of their type, challenging existing theories and the conventional extensile/contractile dichotomy. We trace back the origin of this accumulation behavior to previously overlooked nonlinear active forces using a combination of experiments and a continuous theory derived from a cell-level model. Our findings demonstrate that +1 topological defects can reveal key features of active nematic systems and offer a new way to characterize and classify cell layers.
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