Cell morphogenesis via self-propelled treadmilling actin waves

Actin dynamics mediate cell morphogenesis. Actin filaments polymerize outward at cell protrusions such as the leading edge of migrating cells, thereby pushing the membrane to protrude. The current paradigm explains that actin dynamics are regulated by cell signaling. However, it is unclear how cells spontaneously form actin-based protrusions even without a specific local signaling cue. We found that arrays of treadmilling actin filaments emerge widely in migrating cells and move in the direction of polymerization as actin waves. Their arrival at the cell periphery pushes the plasma membrane to protrude. Furthermore, they accumulate at protrusions without local signaling cues, similar to self-propelled particles colliding with a boundary. This leads to further growth of protrusions, thereby promoting spontaneous formation of the leading edge for migration. We propose that the self-propelled actin waves drive robust formation of protrusions for cell morphogenesis, through their abilities to self-accumulate into protrusions and push the membrane. ### Competing Interest Statement The authors have declared no competing interest.