Patterns make patterns: how hierarchical self-organization couples cell shape to biochemical dynamics

Many biological processes rely on the precise positioning of proteins on the membrane to perform complex tasks. Such protein patterns are susceptible to cell shape changes, raising the question of how these patterns can be robust in a mechanically dynamic environment. Here, we elucidate a mechanism that pattern protein localization on the membrane robustly despite cell shape deformations. By combining experiments in starfish oocytes with mathematical modelling, we find that cell shape information encoded in a cytosolic gradient can be decoded by a bistable front of a RhoA regulator. In turn, this bistable front precisely positions RhoA by locally triggering excitable dynamics. We posit that this hierarchical coupling between a biochemical gradient and protein self-organization provides mechanochemical feedback for cell shape sensing and control.