Speakers

• Prof Colm Kelleher — Syracuse University

Abstract

Spindles are the sub-cellular structures responsible for organizing and segregating chromosomes during cell division. They are composed of microtubules and molecular motors, as well as several other accessory species and complexes. So-called "active matter" theories offer a physical framework for modeling the collective behaviors of self-organized, force-generating ensembles like the spindle, but quantitative applications to living systems remain rare. I will show that a specific class of active matter model -- active liquid crystal theory -- quantitatively predicts steady-state orientation, and that using this theory to interpret polarization microscopy data allows non-invasive measurement of the spindle's collective properties, including elasticity and microtubule transport. Deviations from the theory reveal new biology: chromosomes embedded in the microtubule network act like inclusions and deform the surrounding material, generating micron-scale repulsive forces that produce locally ordered chromosome configurations. Finally, I will discuss current open problems in spindle biophysics, in particular whether active matter theories can capture dynamic behaviors, for example spindle formation (assembly) and chromosome segregation (anaphase).

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