Relaxation and Noise-Driven Oscillations in a Model of Mitotic Spindle Dynamics

by Dionn Hargreaves, Sarah Woolner, and Oliver E. Jensen

Cell division orientation is controlled by the mitotic spindle, which dynamically positions itself to segregate chromosomes. Often, spindle positioning shows noisy, non-linear oscillations, observed here in dividing embryonic epithelial cells. These oscillations are thought to result from molecular motors that randomly attach, walk along, and detach from spindle microtubules. Prior models predict 1D spindle oscillations, but the effects of noise and nonlinearity remain underexplored. We demonstrate that relaxation oscillations emerge when pulling dominates restoring forces provided by flexible microtubules. Stochastic simulations and analysis reveal noise-induced oscillations, offering new insights into oscillation mechanisms.

Force generators (molecular motors) attach, walk along, and detach from microtubules to dynamically position the spindle pole, to give rise to noise-induced oscillations.