Switching Cellular Swirling Upon One-Way Torsional Drive

In understanding how a radially symmetrical actin cytoskeleton spontaneously evolves into a chiral system, here we construct a torsional clutch-filament model for one radial fiber. The model analysis indicates that when actin filaments in growth tend to actively drive the radial fiber to only rotate counter-clockwise, certain amount of passive elastic energy also builds up within the radial fiber upon filament growth, the release of which tends to drive it to rotate clockwise. The competition between these two sources would eventually determine the cellular swirling direction, which can be counter-clockwise or clockwise. The model prediction is in consistency with recent experimental findings. This work provides understanding into how the cellular chirality can be modulated by varied molecular components associated with the cytoskeleton.