Tuning Dynamics of Myosin-Driven Actin-Microtubule Networks

The cytoskeleton, composed of actin, microtubules, and associated motor and binding proteins, is an actively rearranging network with tunable structure and mechanics. For example, myosin motors can induce contraction, extension and flow of actin networks. While actomyosin networks have been well-characterized, the impact of microtubules on actomyosin dynamics remains poorly understood. Here, we create active composite networks of actin and microtubules that exhibit contractile dynamics driven by myosin II. We tune the dynamics, activity and structure of composites by varying the relative concentrations of actin, microtubules, and myosin. Using multi-spectral confocal microscopy, along with differential dynamic microscopy (DDM), particle image velocimetry (PIV), and spatial image autocorrelation (SIA) analyses, we characterize how network composition affects the non-equilibrium dynamics and structure over time. Specifically, we use DDM and PIV to quantify the rate and directionality of network motion, and we use SIA to quantify time-varying network correlation length scales. These results provide new insight into the diverse interactions cells can use to tune activity, as well as the design of tunable active materials.