Confinement-Induced Symmetry Breaking of Active Surfaces

TL;DR

This paper investigates how spatial confinement can induce symmetry breaking in active surfaces like the cell cortex, revealing a transition from symmetric to polarized shapes driven by confinement strength.

Contribution

It introduces a hydrodynamic minimal model showing confinement-induced symmetry breaking in active surfaces, advancing understanding of cell shape changes under spatial constraints.

Findings

Symmetry-breaking transition occurs at a critical confinement level.

Confinement leads to unstable symmetric states and polarized geometries.

The model identifies mechanisms behind confinement-driven symmetry breaking.

Abstract

The actomyosin cortex, a thin layer of a cross-linked polymer network near the cell surface, generates active forces that are responsible for cell shape changes. Many developmental processes that involve such cell shape changes, most prominently embryonic cell division, are spatially confined by eggshells. To investigate the potential role of confinement in redirecting active stresses and enabling symmetry breaking phenomena during cell shape transformations, we study a hydrodynamic minimal model in which the cell cortex is represented as an active fluid surface that undergoes symmetric division in the absence of confinement. When enclosed by an ellipsoidal shell, a spontaneous symmetry-breaking transition emerges at a critical degree of confinement, where symmetrically dividing surfaces become unstable and polarized geometries appear. We show that this transition is controlled by the tightness of the confinement and analyze the solution space of stationary surfaces to identify the mechanisms underlying confinement-induced symmetry breaking.