Active liquid crystal physics governs self-organization of large spindles

While we now possess a nearly complete parts list of the hundreds of proteins and other biomolecules comprising the metazoan spindle, we still lack a quantitative framework for predicting how these components self-organize into cell-scale structures capable of generating and transmitting forces over tens of microns. I will present data and analysis showing that important structural features of steady-state metaphase spindles in living mammalian cells can be understood using concepts and experimental tools from soft-matter physics. In particular, I will show how active liquid-crystal models account for spindle shape and predict large-scale patterns of microtubule orientation within the spindle interior. These models also explain our observations of long-range forces—acting perpendicular to the spindle axis—that apparently act to separate metaphase chromosomes from one another. I will conclude by discussing how these models might be extended to capture dynamic behaviors such as spindle assembly and anaphase.