Active Liquid Crystal Theory Explains the Collective Organization of Microtubules in Human Mitotic Spindles

TL;DR

This paper demonstrates that an active liquid crystal continuum model accurately describes the self-organization, morphology, and dynamics of microtubules in human mitotic spindles, linking microscopic interactions to macroscopic behavior.

Contribution

It introduces a coarse-grained active liquid crystal model that quantitatively predicts spindle morphology and fluctuations, validated by experimental data.

Findings

Model predictions match experimental spindle morphology.

The theory explains microtubule alignment and transport.

Material properties of spindles can be inferred from the model.

Abstract

How thousands of microtubules and molecular motors self-organize into spindles remains poorly understood. By combining static, nanometer-resolution, large-scale electron tomography reconstructions and dynamic, optical-resolution, polarized light microscopy, we test an active liquid crystal continuum model of mitotic spindles in human tissue culture cells. The predictions of this coarse-grained theory quantitatively agree with the experimentally measured spindle morphology and fluctuation spectra. These findings argue that local interactions and polymerization produce collective alignment, diffusive-like motion, and polar transport which govern the behaviors of the spindle's microtubule network, and provide a means to measure the spindle's material properties. This work demonstrates that a coarse-grained theory featuring measurable, physically-interpretable parameters can quantitatively describe the mechanical behavior and self-organization of human mitotic spindles.