Tuning the collective motion of microtubules by their persistence length.

Abstract

Collective motion is an emergent phenomenon of active matter. The collective motion of cytoskeleton filaments, such as motor protein-propelled microtubules and actin filaments, results from their continuous collisions and alignments. However, the detailed emergence mechanism of collective behaviors is still unclear. Notably, the persistence length, an intrinsic mechanical property of filaments determining their orientational flexibility, is likely to directly affect the collective motion. Yet the relevant experimental verifications are still significantly lacking. Here, we investigated how the persistence length of microtubules influences their collective motion using high-density motility gliding assays in the presence of methylcellulose. We found that the collective motion of microtubules can be tuned by their persistence lengths. By combining statistical analysis of collision with an agent-based model, we showed that collectively gliding microtubules with different persistence lengths have distinct local interactions. Stiffer microtubules have more durable alignments after collisions than the softer ones. A detailed analysis of the specific microtubule-microtubule interactions found that - in contrast to the earlier studies - it is not a greater likelihood of alignment after collisions but a more durable alignment that gives rise to enhanced bundling. The persistence length-dependent durability of alignment dominates the collective behavior of microtubules. Moreover, it affects phase transition processes and final coordinated patterns formed during the collective motion.