The dynamics of filament assembly define cytoskeletal network morphology

TL;DR

This paper presents a physical model explaining how actin filament assembly dynamics influence cytoskeletal network structures, revealing a transition between different morphologies driven by polymerization rates.

Contribution

It introduces a novel physical model linking actin assembly dynamics with network morphology, highlighting a transition mechanism based on competition among diffusion, bundling, and steric effects.

Findings

Predicted an abrupt transition between homogeneous and bundled networks.

Identified actin polymerization rate as a key control parameter.

Results align with experimental observations.

Abstract

The actin cytoskeleton is a key component in the machinery of eukaryotic cells, and it selfassembles out of equilibrium into a wide variety of biologically crucial structures. While the molecular mechanisms involved are well characterized, the physical principles governing the spatial arrangement of actin filaments are not understood. Here we propose that the dynamics of actin network assembly from growing filaments results from a competition between diffusion, bundling, and steric hindrance, and is responsible for the range of observed morphologies. Our model and simulations thus predict an abrupt dynamical transition between homogeneous and strongly bundled networks as a function of the actin polymerization rate. This suggests that cells may effect dramatic changes to their internal architecture through minute modifications of their nonequilibrium dynamics. Our results are consistent with available experimental data.