Actomyosin contraction induces droplet motility

TL;DR

This paper presents a minimal model demonstrating how actomyosin contraction within a droplet can generate self-motility, revealing mechanisms of in-bulk cell-like movement driven by contractile gel dynamics.

Contribution

It introduces a novel minimal model linking actomyosin contraction to droplet motility, providing insights into in-bulk cell movement and synthetic active matter design.

Findings

Contractile feedback loop leads to cluster formation and flow enhancement.

Droplet motion can be straight or circular depending on contraction and diffusion balance.

Model offers a framework for studying cell motility and designing synthetic active droplets.

Abstract

While cell crawling on a solid surface is relatively well understood, and relies on substrate adhesion, some cells can also swim in the bulk, through mechanisms that are still largely unclear. Here, we propose a minimal model for in-bulk self-motility of a droplet containing an isotropic and compressible contractile gel, representing a cell extract containing a disordered actomyosin network. In our model, contraction mediates a feedback loop between myosin-induced flow and advection-induced myosin accumulation, which leads to clustering and a locally enhanced flow. Interactions of the emerging clusters with the droplet membrane break flow symmetry and set the whole droplet into motion. Depending mainly on the balance between contraction and diffusion, this motion can be either straight or circular. Our simulations and analytical results provide a framework allowing to study in-bulk myosin-driven cell motility in living cells and to design synthetic motile active matter droplets.