Geometry-induced pulse dynamics in a bulk-surface reaction-diffusion system for cell polarization

TL;DR

This study investigates how cell shape influences localized pattern formation in a reaction-diffusion model for cell polarization, deriving reduced equations to analyze geometry-driven pulse dynamics.

Contribution

The paper introduces a formal reduction of a bulk-surface reaction-diffusion system to ODEs capturing geometry-induced pulse behavior, including stability and bifurcations.

Findings

Geometry affects pulse location and stability.

Bifurcation structures depend on domain shape.

Numerical simulations confirm theoretical predictions.

Abstract

This paper studies a bulk-surface reaction-diffusion system for cell polarization in two-dimensional domains. The model describes the formation of localized patterns through the wave-pinning mechanism, while explicitly incorporating the effect of cell shape. Using singular perturbation methods, we formally derive reduced ordinary differential equations describing the wave-pinning dynamics on a fast time scale and the subsequent slow drift of pulse solutions induced by domain geometry. The resulting slow dynamics is a gradient flow of a potential function whose geometry-dependent part is expressed in terms of the Neumann Green's function. We then analyze the reduced dynamics in several concrete geometries, including dumbbell-shaped domains and perforated disks. In these examples, we characterize stationary pulse positions, their stability, and the bifurcation structures arising from changes in geometric parameters. To evaluate the geometric terms appearing in the reduced dynamics, we use a conformal mapping method to compute the Neumann Green's function for these domains. Our analysis reveals geometry-induced phenomena such as nontrivial stationary pulse locations and both supercritical and subcritical pitchfork bifurcations. Finally, we perform numerical simulations to support the theoretical predictions.