Limiting Effect of Cytoplasmic Volume and Microtubule Dynamics, The

Mitotic spindles play a key role in cellular division. These structures, which are composed of dynamic filaments called microtubules, are responsible for separation and segregation of chromosomes during mitosis. Spindles must be the correct shape and size to insure fidelity of this process, however, their formation and assembly are still not entirely understood. For example, the mechanisms that govern spindle shape and determine individual spindle size for a given cell type are still unknown. Based on evidence from recent studies of spindle scaling, in which spindle size effectively scaled with cell size, we hypothesize that within small cytoplasmic volumes, spindle building blocks become limiting and thereby limit spindle size. This hypothesis predicts that microtubule dynamics within the spindle will be adversely affected by changes in cytoplasmic volume. By combining cell-free cytoplasmic extracts, microfluidics, and confocal microscopy, we hope to measure changes in microtubule dynamics and elucidate the relationship between cell volume and spindle size within the cell.