Tuning the mechanochemical machinery in oocytes using light.

Cellular development often involves a series of robust events that are elaborately coordinated by coupled biochemical and mechanical regulation. Surface contraction waves (SCW) in starfish oocytes post anaphase is a canonical example of such complex mechanochemical feedback. During these contraction waves, Rho-GTPase pathway dynamics and mechanical deformations mutually crosstalk, constituting the oocyte as an active biological material capable of forming self-organized spatiotemporal patterns. Though molecular players are broadly known, the detailed physical mechanisms of SCW are still unexplored due to a lack of perturbative methods in this mechanochemical system. Here, we report the implementation of a light-mediated molecular switch in the starfish Rho GTPase activation pathway that allows for versatile spatiotemporal manipulation of Rho recruitment. By precisely controlling the Rho activation sites and the resulting oocyte contraction patterns, we can explore with vast flexibility the interplay between biochemical and mechanical regulators. This framework will facilitate a quantitative understanding of the underlying physical mechanism driving SCW.