Mathematical Model Explains How Cells Spontaneously Initiate Crawling Motion Through Actin Polarization
Researchers have proposed a one-dimensional continuum model showing how cells can spontaneously initiate crawling motion driven purely by actin polymerization and chemical feedback, without requiring molecular motors or pre-existing polarity. The model centers on a feedback loop between cell movement, an external chemical regulator of actin nucleation, and polymerization at cell edges, which breaks symmetry and sustains directed motion above a critical activity threshold. The findings suggest a generic, minimal mechanism for cell motility that could reshape understanding of how cells polarize and move in biological contexts.
A new theoretical study posted to arXiv proposes a minimal one-dimensional continuum model for how cells can spontaneously begin crawling on rigid substrates through protrusion alone. The model represents the cell cytoskeleton as a viscous actin meshwork that turns over in the bulk and polymerizes at two moving cell edges. Symmetry breaking emerges from a feedback loop: when the cell moves, an external chemical regulator of actin nucleation becomes polarized near the moving boundaries, imposing different nucleation densities at the two edges, which generates unequal protrusive forces that reinforce motion and sustain polarization. Above a critical protrusive activity, the static symmetric state becomes unstable and the system bifurcates to a motile polarized state; depending on how the external cue controls nucleation, this transition can be supercritical or subcritical, with the latter allowing coexistence of static and motile states. Calibrated to keratocyte cell parameters, the model reproduces realistic crawling speeds and actin-density profiles, including asymmetric edge-localized density peaks. Notably, the mechanism requires neither molecular motors, specific adhesion dynamics, deformable substrates, nor pre-existing polarity, suggesting it represents a broadly applicable route to spontaneous cell motility.
What's missing
The model is strictly one-dimensional and has not yet been validated against three-dimensional cell geometries or experimental perturbation data. The identity and specific biochemical nature of the proposed 'external chemical regulator' of actin nucleation are not specified, leaving open questions about which molecular candidates could play this role in vivo. The study has not yet undergone peer review.
What different sources said
- arXiv physicsCenter
Spontaneous polarization for protrusion-driven cell crawling
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