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Related Concept Videos

Spindle Assembly02:50

Spindle Assembly

Spindle assembly occurs through three, often coexisting, pathways – the centrosome-mediated pathway, the chromatin-mediated pathway, and the microtubule-mediated pathway – collectively contributing to form a robust spindle apparatus.
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
Spindle Assembly02:50

Spindle Assembly

Spindle assembly occurs through three, often coexisting, pathways – the centrosome-mediated pathway, the chromatin-mediated pathway, and the microtubule-mediated pathway – collectively contributing to form a robust spindle apparatus.
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...
Forces Acting on Chromosomes02:11

Forces Acting on Chromosomes

During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis. 
Microtubules and motor proteins exert two types of forces on...
Forces Acting on Chromosomes02:11

Forces Acting on Chromosomes

During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis. 
Microtubules and motor proteins exert two types of forces on...
Anaphase A and B01:39

Anaphase A and B

Microtubules form through the end-to-end polymerization of tubulin heterodimers. Kinetochore microtubules originate from the spindle poles, and their plus-ends connect with the kinetochores on sister-chromatids. Ndc80 protein complexes, present on the kinetochore, form low-affinity links with the plus end of these kinetochore microtubules.
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...
Anaphase A and B01:39

Anaphase A and B

Microtubules form through the end-to-end polymerization of tubulin heterodimers. Kinetochore microtubules originate from the spindle poles, and their plus-ends connect with the kinetochores on sister-chromatids. Ndc80 protein complexes, present on the kinetochore, form low-affinity links with the plus end of these kinetochore microtubules.
Plus-end depolymerization releases tubulin heterodimers from the terminal region of the microtubule. As tubulin subunits are lost, the Ndc80 complexes detach...

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Related Experiment Video

Updated: Jun 25, 2026

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
10:52

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets

Published on: August 13, 2016

Kinetochore-generated pushing forces separate centrosomes during bipolar spindle assembly.

Alberto Toso1, Jennifer R Winter, Ainslie J Garrod

  • 1Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland.

The Journal of Cell Biology
|February 11, 2009
PubMed
Summary

Kinetochores help separate cell poles for proper division by pushing microtubules apart. This mechanism is vital when aurora A is inhibited, revealing two pathways for cell division.

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Self-Assembly of Microtubule Tactoids
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Last Updated: Jun 25, 2026

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
10:52

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets

Published on: August 13, 2016

Directly Measuring Forces Within Reconstituted Active Microtubule Bundles
07:47

Directly Measuring Forces Within Reconstituted Active Microtubule Bundles

Published on: May 10, 2022

Self-Assembly of Microtubule Tactoids
08:49

Self-Assembly of Microtubule Tactoids

Published on: June 23, 2022

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Bipolar spindle formation in animal somatic cells requires centrosome separation.
  • Centrosome separation is regulated by pathways including cortical forces and microtubule (MT) sliding, influenced by the protein kinase aurora A.
  • Previous findings showed Mcm21R (CENP-O) depletion leads to monopolar spindles, suggesting a role for kinetochores in centrosome separation.

Purpose of the Study:

  • To investigate the contribution of kinetochores to centrosome separation during cell division.
  • To elucidate the mechanism by which kinetochores influence centrosome separation.
  • To determine if kinetochores play a role in centrosome separation, particularly when aurora A activity is compromised.

Main Methods:

  • Depletion of the human kinetochore protein Mcm21R (CENP-O).
  • Microscopy techniques to observe spindle formation and centrosome separation.
  • Inhibition of aurora A to assess the interplay between pathways.

Main Results:

  • Kinetochores exert a pushing force on kinetochore fibers (k-fibers) after nuclear envelope breakdown, promoting centrosome separation.
  • This force relies on poleward microtubule (MT) flux at k-fiber plus ends, requiring stable k-fibers.
  • The kinetochore-dependent force is crucial for centrosome separation when aurora A is inhibited.

Conclusions:

  • Two distinct mechanisms control centrosome separation during prometaphase: an aurora A-dependent pathway and a kinetochore-dependent pathway.
  • The kinetochore pathway utilizes pushing forces generated by k-fibers.
  • Kinetochores are essential for proper bipolar spindle formation, especially under conditions of aurora A inhibition.