Computational model of mitotic spindle positioning in polarized cells

The microtubule cytoskeleton plays important roles during the cell life cycle, in events including mitotic spindle assembly, chromosome segregation, nuclear elongation, and spindle positioning. During cell division in budding yeast, interactions between astral microtubules and proteins at the cell cortex position the spindle and nucleus at the bud neck before cytokinesis. The spindle moves due to pulling forces on the microtubules generated by the minus-end-directed motor dynein, which are activated by binding to protein domains localized at the cell cortex. Both the asymmetric distribution of cortical dynein binding domains and microtubule buckling and stabilization are thought to be important for regulating spindle positioning, but how the interplay between microtubule dynamics and motor-driven pulling forces lead to proper positioning at the site of cytokinesis is not well understood. We present results from simulations of a minimal spindle positioning model in a polarized cell driven by interactions between astral filaments, motorized tethers, and cortical binding domains. Our results show how binding domain localization and filament dynamics affect spindle positioning in polarized cells.