Polarity patterns of stress fibers

TL;DR

This paper models the polarity patterns of stress fibers in cells using thermodynamics, revealing that active contractility is essential for the formation of alternating polarity patterns, with a transition characterized as a nonequilibrium Lifshitz point.

Contribution

It introduces a thermodynamic framework to describe stress fiber polarity patterns and identifies active contractility as crucial for alternating patterns.

Findings

Transition from graded to alternating polarity is a nonequilibrium Lifshitz point.

Active contractility is necessary for sarcomeric, alternating polarity patterns.

The model predicts conditions for different polarity pattern formations.

Abstract

Stress fibers are contractile actomyosin bundles commonly observed in the cytoskeleton of metazoan cells. The spatial profile of the polarity of actin filaments inside contractile actomyosin bundles is either monotonic (graded) or periodic (alternating). In the framework of linear irreversible thermodynamics, we write the constitutive equations for a polar, active, elastic one-dimensional medium. An analysis of the resulting equations for the dynamics of polarity shows that the transition from graded to alternating polarity patterns is a nonequilibrium Lifshitz point. Active contractility is a necessary condition for the emergence of sarcomeric, alternating polarity patterns.