Self-organized patterning of the cell cortex

The cortical actomyosin cytoskeleton is the primary driver of cell shape changes. The Rho GTPases regulate cortical actomyosin by forming dynamic, periodic patterns such as pulses and traveling waves which are converted into pulses and waves of cytoskeletal changes by proteins (effectors) that signal from the Rho GTPases to the cytoskeleton. Recent evidence indicates that the periodic Rho patterns arise by self-organization based on fast positive feedback and delayed negative feedback. Consistent with this model, we find that the natural wave regulators can induce propagating waves of Rho activity in cells that do not normally have them (Xenopus oocytes), but only when such regulators can engage in positive and negative feedback. Further, synthetic proteins engineered to provide fast positive feedback and delayed negative feedback can also induce traveling Rho waves in the Xenopus oocyte system. Strikingly, the waves produced naturally or synthetically vary in predictable ways, a finding that we are currently trying to understand.