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Related Concept Videos

The Mitotic Spindle02:27

The Mitotic Spindle

The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
The Mitotic Spindle02:27

The Mitotic Spindle

The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures bipolar mitotic...
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...
Microtubule Associated Proteins (MAPs)01:42

Microtubule Associated Proteins (MAPs)

Microtubule function and architecture are regulated by an array of specialized proteins called microtubule-associated proteins or MAPs. These proteins are widespread across different organisms and have conserved protein motifs, like the multi-TOG domain for tubulin binding found in the CLASP family of MAPs. Some MAPs are lineage-specific based on their conserved domains. Their functions depend upon the cytoskeletal architecture and cell type they are located within. In-plant cells, a specific...
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...
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: Jul 5, 2026

Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations
07:14

Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations

Published on: September 20, 2019

The RanGTP gradient - a GPS for the mitotic spindle.

Petr Kalab1, Rebecca Heald

  • 1Laboratory of Cell and Molecular Biology, National Cancer Institute, Bethesda, MD 20892-4256, USA. pkalab@yahoo.com

Journal of Cell Science
|May 13, 2008
PubMed
Summary
This summary is machine-generated.

The GTPase Ran protein gradient acts as a genome-positioning system (GPS) crucial for cell division. This system guides spindle assembly and genome segregation during mitosis, ensuring proper cell function.

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Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
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Related Experiment Videos

Last Updated: Jul 5, 2026

Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations
07:14

Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations

Published on: September 20, 2019

Measurement of Microtubule Dynamics by Spinning Disk Microscopy in Monopolar Mitotic Spindles
08:31

Measurement of Microtubule Dynamics by Spinning Disk Microscopy in Monopolar Mitotic Spindles

Published on: November 15, 2019

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

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • The GTPase Ran is essential for nuclear transport, mitosis, and nuclear envelope formation.
  • Ran's activity is regulated by RCC1 and RanGAP, creating a RanGTP gradient.
  • This gradient functions as a genome-positioning system (GPS) in eukaryotic cells.

Purpose of the Study:

  • To elucidate the mechanisms by which the RanGTP gradient directs cellular functions, particularly during mitosis.
  • To understand how RanGTP binding to nuclear transport receptors (NTRs) influences downstream processes.
  • To investigate the role of the Ran-dependent GPS in mitotic spindle assembly and genome segregation.

Main Methods:

  • Fluorescence resonance energy transfer (FRET) imaging to visualize molecular interactions and gradients.
  • Computational modeling to simulate and analyze the RanGTP gradient dynamics.
  • Biochemical assays to study the interactions between RanGTP, NTRs, and spindle assembly factors (SAFs).

Main Results:

  • The RanGTP gradient spatially directs genome segregation by the mitotic spindle.
  • RanGTP binding to importins and subsequent release of SAFs activates microtubule organization.
  • Bipolar spindle assembly is robustly achieved through cooperativity and positive feedback within the Ran-activated SAF network.

Conclusions:

  • The Ran-dependent GPS is a conserved mechanism critical for accurate chromosome segregation during mitosis.
  • RanGTP gradients spatially regulate essential cellular processes, including spindle assembly and nuclear transport.
  • Further research is needed to fully understand the diverse roles of the RanGTP gradient across different cell types and species.