Active mechanics of starfish oocytes

During meiosis, starfish oocytes exhibit a dramatic surface contraction wave characterized by a band of large-scale deformation traveling from the vegetal pole to the animal pole. This inherently mechanical process is driven by active stresses generated by actomyosin contraction. What are the mechanical properties of these oocytes? How can modulating cytoskeletal organization affect the emergent mechanics and the contraction wave dynamics? Here, we present experimental results beginning to address these questions. Using micropipette aspiration, we find that the mechanical properties are well described by a modified Maxwell model, allowing us to quantitatively measure the viscosity, surface tension, and elastic modulus. These mechanical measurements are complemented by work combining quantitative light microscopy and pharmacological inhibition to assess cytoskeletal contributions to the emergent contraction wave dynamics. For example, using the actin inhibitor cytochalasin D, we find a dose dependent decrease in the magnitude of the contraction. This work represents a step towards understanding cytoskeletal contributions to the emergent dynamics and mechanics in starfish oocytes and in actin cortices more generally.