Active Restructuring of Myosin-Driven Actin-Microtubule Networks

The cytoskeleton is a dynamic network of protein filaments and motors, including actin, microtubules and myosin, that enable key processes in the cell such as growth, movement, and cell division. Active rearrangement and contraction of actin networks by myosin motors has been extensively studied in recent years. However, how the interactions between actin and microtubules affects actomyosin activity remains poorly understood. We investigate the active dynamics and restructuring of composite networks of actin and microtubules driven by myosin II motors. We combine spatial image autocorrelation analysis and particle image velocimetry to characterize the time-varying network structure and velocity profiles of actin and microtubules. We show that actin and microtubules exhibit similar contractile flow fields that increase in magnitude and heterogeneity as the concentration of actin or myosin increases. We also find that the correlation length scales of the composite networks generally decrease over time but at a slower rate with higher concentrations of actin or myosin. These findings provide insight into how the cytoskeleton can tune its dynamics and structure to impact cellular processes such as movement and growth.