Size scaling of microtubule asters in confinement

ORAL

Abstract

Microtubule asters are radial arrays of microtubules (MTs) nucleated around organizing centers (MTOCs). Across a wide range of cell types and sizes, aster positioning influences cellular organization. To investigate aster size and positioning, we reconstituted dynamic asters in \textit{Xenopus} cytoplasmic extract, confined in fluorous oil microfluidic emulsions. In large droplets, we observed centering of MTOCs. In small droplets, we observed a breakdown in natural positioning, with MTOCs at the droplet edge and buckled or bundled MTs along the interface. In different systems, asters are positioned by different forces, such as pushing due to MT polymerization, or pulling due to bulk or cortical dynein. To estimate different contributions to aster positioning, we biochemically perturbed dynactin function, or MT or actin polymerization. We used carbon nanotubes to measure molecular motions and forces in asters. These experimental results inform quantitative biophysical models of aster size and positioning in confinement.

–

Authors

  • James Pelletier

    Dept., of Physics, Massachusetts Institute of Technology, Dept., of Systems Biology, Harvard Medical School

  • Christine Field

    Dept., of Systems Biology, Harvard Medical School

  • Kaspars Krutkramelis

    Dep., of Chemical Engineering, University of Wyoming

  • Nikta Fakhri

    Massachusetts Inst of Tech-MIT, Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology, USA, Dept., of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology

  • John Oakey

    Dept., of Chemical Engineering, University of Wyoming

  • Jay Gatlin

    Dept., of Molecular Biology, University of Wyoming

  • Timothy Mitchison

    Dept., of Systems Biology, Harvard Medical School