A computational model of cell polarization and motility coupling mechanics and biochemistry. Multiscale Modeling

Abstract. The motion of a eukaryotic cell presents a variety of interesting and challenging problems from both a modeling and a computational perspective. The processes span many spatial scales (from mole-cular to tissue) as well as disparate time scales, with reaction kinetics on the order of seconds, and the deforma-tion and motion of the cell occurring on the order of minutes. The computational difficulty, even in two dimensions, resides in the fact that the problem is inherently one of deforming, nonstationary domains, bounded by an elastic perimeter, inside of which there is redistribution of biochemical signaling substances. Here we report the results of a computational scheme using the immersed-boundary method to address this problem. We adopt a simple reaction-diffusion (RD) system that represents an internal regulatory mechanism controlling the polarization of a cell and determining the strength of protrusion forces at the front of its elastic perimeter. Using this computational scheme we are able to study the effect of protrusive and elastic forces on cell shapes on their own, the distribution of the RD system in irregular domains on its own, and the coupled mechanical-chemical system. We find that this representation of cell crawling can recover important aspects of the spontaneous polarization and motion of certain types of crawling cells. Key words. 2D eukaryotic cell motility, simulation, immersed-boundary method, tension, protrusion, reaction-diffusion system, deforming domain, polarization, wave-pinning, elastic perimete