A two-dimensional continuum model for the crawling nematode sperm cell

Abstract

Migration of animal cells is the most striking process underlying the phenomena of wound healing, morphogenesis and cancerogenesis. Despite radical advances in cell biology and biophysics, we still do not have a complete picture of how animal cells move across surfaces. Motility for many of these cells involves a multitude of molecular mechanisms, and we do not yet know how they are integrated at the cellular level. Because of this, simple and specialized cells, like the sperm of Ascaris suum (A. suum) have attracted the attention of researchers. They appear to be dedicated solely to migration, and the locomotion machinery has been dramatically simplifi ed. Nematode sperm cells recycle major sperm protein from dimers into fi lament networks, as their hydrophobic patches come into contact with each other. These cells look and move much like similarly shaped actin-based cells, so that understanding their locomotion will elucidate general principles of migrating animal cells.This paper develops a two-dimensional (2-D) model of motility for the sperm of A. suum, in a polar coordinate system, for a continuous density of bundled fi laments, free dimers and crosslinks. Simulations recover bundle densities, crawling speeds and cell shapes observed in recent experiments for both turning and steady-state motion.