Tunable Non-Equilibrium Dynamics of Motor-Driven Cytoskeleton Composites

Motor-driven scaffolds of actin filaments and microtubules display rich non-equilibrium dynamics and structure that are critical to mesoscale cellular behavior. Numerous studies have investigated the dynamics of actomyosin networks, active kinesin-microtubule systems, and steady-state actin-microtubule composites. Yet, in cells all of these components interact to enable the diverse processes and properties that cells exhibit. Here, we create in vitro actin-microtubule networks driven by myosin-II minifilaments and quad-headed kinesin clusters, and use multi-color confocal microscopy to image the active composites. To characterize the non-equilibrium dynamics of actin and microtubules in the composites, we use differential dynamic microscopy (DDM) to quantify filament contraction and flow as the composites dynamically restructure. We find that myosin and kinesin activity lead to dramatically different dynamics of both filaments, and that static crosslinking of either filament changes the patterns and rates of motor-driven restructuring.