Size-regulated symmetry breaking in reaction-diffusion models of developmental transitions

TL;DR

This paper explores how size-dependent symmetry breaking in reaction-diffusion models can regulate the timing of developmental transitions in multicellular organisms, proposing a minimal framework linking pattern formation to developmental timing.

Contribution

It introduces a minimal mass-conserved reaction-diffusion model demonstrating how system size influences symmetry breaking and developmental timing, unifying patterning and timing mechanisms.

Findings

Three distinct behaviors: clock-, timer-, and switch-like dynamics.

Size-dependent patterning influences developmental transition timing.

Model aligns with experimental observations of developmental processes.

Abstract

The development of multicellular organisms proceeds through a series of morphogenetic and cell-state transitions, transforming homogeneous zygotes into complex adults by a process of self-organization. Many of these transitions are achieved by spontaneous symmetry breaking mechanisms, allowing cells and tissues to acquire pattern and polarity by virtue of local interactions without an upstream supply of information. The combined work of theory and experiment has elucidated how these systems break symmetry during developmental transitions. Given such transitions are multiple and their temporal ordering is crucial, an equally important question is how these developmental transitions are coordinated in time. Using a minimal mass-conserved substrate-depletion model for symmetry breaking as our case study, we elucidate mechanisms by which cells and tissues can couple reaction-diffusion driven symmetry breaking to the timing of developmental transitions, arguing that the dependence of patterning mode on system size may be a generic principle by which developing organisms measure time. By analyzing different regimes of our model, simulated on growing domains, we elaborate three distinct behaviours, allowing for clock-, timer-, or switch-like dynamics. By relating these behaviours to experimentally documented case studies of developmental timing, we provide a minimal conceptual framework to interrogate how developing organisms coordinate developmental transitions.