Figure 1.

Characterization of the cell polarization occurring before migration in the mechanochemical cell migration model. (a) The schematic diagram of the regulatory network in the model of cell migration is given. Cell tension (mt) globally inhibits (denoted by —|) the formation of F-actin (f) in the cell. However, F-actin polymerization increases (black solid arrow →) the cortical part of cell tension and meanwhile activates the membrane-bound Rac-GTP (u) (light blue). Rac-GTP is also activated by stimulation and itself. In addition, Rac-GTP on the membrane and Rac-GDP (v) in the cytosol interconvert. Myosin (m) attached to the actin bundles is mutually antagonized with F-actin. (b) The steady-state spatial profiles of F-actin in a polarized cell with initial line tension σ = 0.2 and 0.8 pN/μm, respectively, are shown. To respond to a gradient external stimulus, F-actin accumulates at the cell front in the cytoplasm. As σ rises to 0.8 pN/μm, the maximum concentration of F-actin decreases. (c) The threshold of the amplitude of stimuli as a function of the duration of stimuli for inducing cell polarity at different values of initial line tension is shown. (d) The fraction of polarized cells under various values of σ is shown. Each bar counts the results from repetitive simulations under the sample size N = 20. To see this figure in color, go online.