Actomyosin-driven mechanics of starfish oocytes

Actomyosin network contractility is a crucial driver of force generation in eukaryotic cells. These networks are driven out of equilibrium in part by the molecular motor myosin which crosslinks and exerts forces on actin filaments. While myosin's role in force generation is well studied, the mechanism by which these forces drive cellular-scale deformation is still debated. As a step towards addressing this, we here consider the actomyosin-driven surface contraction wave of meiotic starfish oocytes. Using pharmacological inhibitions targeting actin polymerization, we find that cellular deformation during the contraction wave is not a monotonic function of cortical actin density but is instead peaked near the wild-type density. This surprising observation provides a window to test the mechanisms underlying actomyosin contractility. We’re using a combination of targeted biochemical perturbations, agent-based simulations, and theoretical modeling to understand this phenomenon.