Collective dynamics of active cytoskeletal networks

TL;DR

This study investigates the collective behavior of active cytoskeletal networks using an in vitro model of actin, fascin, and myosin-II, revealing pulsative dynamics driven by molecular interactions and force competition.

Contribution

It introduces a minimal in vitro model system demonstrating pulsative collective dynamics and links these behaviors to molecular force interactions and feedback mechanisms.

Findings

Networks exhibit alternating runs and stalls with superdiffusive motion.

Collective dynamics depend on the relative binding strength of myosin-II to actin.

Simulations based on simple interaction rules support experimental observations.

Abstract

Self organization mechanisms are essential for the cytoskeleton to adapt to the requirements of living cells. They rely on the intricate interplay of cytoskeletal filaments, crosslinking proteins and molecular motors. Here we present an in vitro minimal model system consisting of actin filaments, fascin and myosin-II filaments exhibiting pulsative collective long range dynamics. The reorganizations in the highly dynamic steady state of the active gel are characterized by alternating periods of runs and stalls resulting in a superdiffusive dynamics of the network's constituents. They are dominated by the complex competition of crosslinking molecules and motor filaments in the network: Collective dynamics are only observed if the relative strength of the binding of myosin-II filaments to the actin network allows exerting high enough forces to unbind actin/fascin crosslinks. The feedback between structure formation and dynamics can be resolved by combining these experiments with phenomenological simulations based on simple interaction rules.