Active Cytoskeletal Composites Display Emergent Tunable Contractility and Restructuring

TL;DR

This study combines experiments and modeling to understand how actin, microtubules, and myosin interact to produce tunable contractility and restructuring in cytoskeletal composites, revealing principles for designing adaptable active materials.

Contribution

It provides new insights into the interplay of actin, microtubules, and myosin in active matter, highlighting conditions for emergent contractility and resilience in cytoskeleton-inspired materials.

Findings

Ballistic contraction occurs with sufficient flexibility and motor density.

A critical fraction of microtubules is needed for controlled dynamics.

Networks with balanced actin and microtubules resist stress and support restructuring.

Abstract

The cytoskeleton is a model active matter system that controls diverse cellular processes from division to motility. While both active actomyosin dynamics and actin-microtubule interactions are key to the cytoskeleton's versatility and adaptability, an understanding of their interplay is lacking. Here, we couple microscale experiments with mechanistic modeling to elucidate how connectivity, rigidity, and force-generation affect emergent material properties in in vitro composites of actin, tubulin, and myosin. We use time-resolved differential dynamic microscopy and spatial image autocorrelation to show that ballistic contraction occurs in composites with sufficient flexibility and motor density, but that a critical fraction of microtubules is necessary to sustain controlled dynamics. Our active double-network models reveal that percolated actomyosin networks are essential for contraction, but that networks with comparable actin and microtubule densities can uniquely resist mechanical stresses while simultaneously supporting substantial restructuring. Our findings provide a much-needed blueprint for designing cytoskeleton-inspired materials that couple tunability with resilience and adaptability.