Self-organization of kinetochore-fibers in human mitotic spindles

Elife. 2022 Jul 25:11:e75458. doi: 10.7554/eLife.75458.

Abstract

During eukaryotic cell division, chromosomes are linked to microtubules (MTs) in the spindle by a macromolecular complex called the kinetochore. The bound kinetochore microtubules (KMTs) are crucial to ensuring accurate chromosome segregation. Recent reconstructions by electron tomography (Kiewisz et al., 2022) captured the positions and configurations of every MT in human mitotic spindles, revealing that roughly half the KMTs in these spindles do not reach the pole. Here, we investigate the processes that give rise to this distribution of KMTs using a combination of analysis of large-scale electron tomography, photoconversion experiments, quantitative polarized light microscopy, and biophysical modeling. Our results indicate that in metaphase, KMTs grow away from the kinetochores along well-defined trajectories, with the speed of the KMT minus ends continually decreasing as the minus ends approach the pole, implying that longer KMTs grow more slowly than shorter KMTs. The locations of KMT minus ends, and the turnover and movements of tubulin in KMTs, are consistent with models in which KMTs predominately nucleate de novo at kinetochores in metaphase and are inconsistent with substantial numbers of non-KMTs being recruited to the kinetochore in metaphase. Taken together, this work leads to a mathematical model of the self-organization of kinetochore-fibers in human mitotic spindles.

Keywords: cell biology; human; kinetochore; microtubule; mitosis; physics of living systems; self-organization; spindle.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chromosome Segregation
  • Chromosomes
  • Humans
  • Kinetochores*
  • Metaphase
  • Microtubules / metabolism
  • Mitosis
  • Spindle Apparatus* / metabolism

Associated data

  • Dryad/10.5061/dryad.69p8cz948

Grants and funding

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.