A dissipative mass conserved reaction-diffusion system reveals switching between coexisting polar and oscillatory cell motility states.

Motile eukaryotic cells display distinct modes of migration that often occur within the same cell type. It remains unclear, however, whether transitions between the migratory modes require changes in external conditions, or whether the different modes are coexisting states that emerge from the underlying signaling network. Using a simplified mass-conserved reaction-diffusion model of small GTPase signaling with F-actin mediated feedback, we uncover a distinct bistable mechanism (involving gradient-like phase-separation and traveling waves) and a regime where a polarized mode of migration coexists with spatiotemporal oscillations; the latter, in larger domains, including in three-dimensional surface geometry, result in disordered patterns even in the absence of noise or shape deformations. Indeed, experimental observations of Dictyostelium discoideum show that, upon collision with a rigid boundary, cells may switch from polarized to disordered motion.