Directed cell migration from protrusion-adhesion coupling under local chemotactic regulation

Directed cell migration in response to chemical cues is central to development, immunity, and cancer invasion. While many models assume predefined cell polarity or directional sensing, experiments suggest that persistent migration may emerge from local mechanical interactions. Here, we present a minimal two-dimensional mechanical model in which stochastic protrusion dynamics, discrete adhesion formation, and substrate-mediated force transmission collectively generate persistent and directed cell migration. Chemotactic signals locally regulate protrusion growth and traction forces without imposing any predefined global polarity axis or migration trajectory. The model reproduces robust chemotactic behaviors, including persistent polarization and source-oriented trajectories. Control simulations show that both chemotactic regulation and adhesion-mediated force transmission are necessary for efficient directed migration. In addition, comparisons between regular and random adhesion networks at similar adhesion density reveal that substrate disorder primarily increases trajectory-to-trajectory variability without significantly altering average migration efficiency, persistence, or chemotactic performance. Overall, these results demonstrate how a minimal mechanically explicit framework can isolate the contribution of local protrusion-adhesion interactions to emergent migration dynamics.