Fig. 4. Polarized actin turnover governs a transition between actin recirculation and unidirectional transport.

a, Incorporating F-actin depolymerization and anterior polymerization into the model enables the emergence of a unidirectional, stable velocity pattern. b, Tuning rates of F-actin polymerization and depolymerization move the cell between distinct self-organized states: bidirectional cyclosis, unidirectional and disorganized. c, Model prediction: recirculating F-actin cyclosis generates bidirectional traction force (blue arrows) to drive ‘patch’ gliding. d–f, Model prediction: the unidirectional self-organized F-actin state drives helical gliding (d), circular gliding (e) and twirling (f). In the images in c–f, cells are viewed from below; cell-substrate contact occurs at the position of the inferred traction force.