Scaling behavior in contractile actomyosin networks with turnover

The actomyosin cytoskeleton plays an essential role in many basic cellular processes including polarization, cell shape determination and movement. From a physical perspective, the cytoskeleton is an excellent model system to study collective behavior in far-from-equilibrium active matter. In my research, I study reconstituted 3D actomyosin networks that undergo rapid turnover within cell-sized water-in-oil droplets. Within minutes, the networks reach a dynamic steady-state with spherically-symmetric, myosin-driven, inward contractile flow which is balanced by outward diffusive flux of dissociated network components. We identify scaling behavior emerging for a wide range of physiological conditions where the networks exhibit homogenous, density-independent, contraction indicating that the active stress driving contraction and the effective network viscosity scales similarly with network density. Moreover, we find that the contraction rate is roughly proportional to the network disassembly rate, but this relation breaks down in the presence of excessive crosslinking or branching in the network. Our findings serve as a basis for the development of a quantitative theoretical model for the actomyosin network as an active gel.