Cell motility resulting from spontaneous polymerization waves.

The crawling of cells on a substrate is in many cases driven by the actin cytoskeleton. How actin filaments and associated proteins are organized to generate directed motion is still poorly understood. Recent experimental observations suggest that spontaneous cytoskeletal waves might orchestrate the actin-filament network to produce directed motion. We investigate this possibility by studying a mean-field description of treadmilling filaments interacting with nucleating proteins, a system that is known to self-organize into waves. Confining the system by a boundary that shares essential features of membranes, we find that spontaneous waves can generate directional motion. We also find that it can produce lateral waves along the confining membrane as are observed in spreading cells.