Topology Governs the Presence and Timescale of Anomalous DNA Transport Across Cytoskeletal Networks

The cytoskeleton--a polymerous composite of microtubules, actin, and other proteins--is one of many non-equilibrium systems characterized as active matter. In the cytoskeleton, motor proteins (such as kinesin) consume energy from their environment to push and pull on the network's polymers, instigating various forms of flow and contraction that make the transport dynamics across the composite challenging to understand. Here, we investigate the effect of DNA topology on its transport within reconstituted cytoskeletal networks of microtubules and kinesin. We leverage epifluorescence microscopy and single-particle tracking to examine the transport of circular DNA, linear DNA, and fluorescent microspheres in both non-active and active networks. Our findings reveal that there exist clear differences in transport dynamics for the three particle types, as shown by their anomalous scaling exponent (α) distributions. In non-active networks, the circular DNA contains a subdiffusive population not present in the linear DNA or the microspheres. In active networks, all three particle types exhibit a similar transition from Brownian to directed motion, but the circular topology transitions faster than the linear, which in turn transitions faster than the microspheres. Collectively, our results strongly suggest that threading is a physical mechanism at play in the transport of DNA across cytoskeletal networks, which has implications for many biological and industrial processes.