Active contractility in actomyosin networks

TL;DR

This paper presents a microscopic model of actomyosin networks that explains how motor concentration and filament properties lead to active contractility, aligning with experimental observations of force generation and network behavior.

Contribution

The study introduces a dynamic model incorporating load response and motor-driven filament sliding, elucidating the collective behavior leading to contractility in actomyosin networks.

Findings

Model captures formation and dynamics of contractile structures.

Active contractility depends on motor concentration and filament susceptibility.

Cooperative motor action leads to global contractility via active coarsening.

Abstract

Contractile forces are essential for many developmental processes involving cell shape change and tissue deformation. Recent experiments on reconstituted actomyosin networks, the major component of the contractile machinery, have shown that active contractility occurs above a threshold motor concentration and within a window of crosslink concentration. We present a microscopic dynamic model that incorporates two essential aspects of actomyosin self-organization: the asymmetric load response of individual actin filaments and the correlated motor-driven events mimicking myosin-induced filament sliding. Using computer simulations we examine how the concentration and susceptibility of motors contribute to their collective behavior and interplay with the network connectivity to regulate macroscopic contractility. Our model is shown to capture the formation and dynamics of contractile structures and agree with the observed dependence of active contractility on microscopic parameters including the contractility onset. Cooperative action of load-resisting motors in a force-percolating structure integrates local contraction/buckling events into a global contractile state via an active coarsening process, in contrast to the flow transition driven by uncorrelated kicks of susceptible motors.