Michael Murrell

 

Michael Murrell, Yale

Isotropic Actomyosin Promotes Telescopic Contractility

Myosin-II induced mechanical stresses within the F-actin cortex mediate cortical flows and cell shape changes.  While the molecular interactions between individual myosin motors and F-actin are known, how the accumulation and transmission of the resultant active stresses depend on F-actin architecture in living cells is poorly understood.  Here, we explore the accumulation of myosin-induced mechanical stresses within a 2D model of the isotropic actomyosin cytoskeleton, where myosin activity is controlled spatially and temporally using light.  By controlling the shape and the duration of myosin activity on cellular length-scales, we show that contractility of isotropic actomyosin is highly cooperative, telescopic with the area and generates a spatial pattern of mechanical stresses consistent with that observed in contractile cells with organized F-actin architecture.  We quantitatively reproduce these behaviors using an isotropic active gel model of the cytoskeleton, and elucidate their mechanical origins using agent-based simulations.