Related Experiment Video

Updated: May 13, 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

Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes

Kexi Yi1, Boris Rubinstein, Jay R Unruh

  • 1Stowers Institute for Medical Research, Kansas City, MO 64110, USA.

The Journal of Cell Biology
|February 27, 2013
PubMed

Insights

Mouse oocyte maturation relies on asymmetric spindle positioning. This study reveals two actin nucleators, Fmn2 and Arp2/3 complex, drive biphasic chromosome migration via distinct actin-based forces.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Reproductive Biology

Background:

  • Polar body extrusion in oocytes requires asymmetric meiotic spindle positioning.
  • Spindle migration from the oocyte interior to the subcortical region is crucial for this process.

Purpose of the Study:

  • To elucidate the molecular mechanisms driving meiosis I spindle migration in mouse oocytes.
  • To identify the key regulators of asymmetric spindle positioning during oocyte maturation.

Main Methods:

  • Investigated actin dynamics and spindle behavior during oocyte maturation.
  • Utilized live-cell imaging and genetic manipulation to study actin nucleators Fmn2 and Arp2/3 complex.
  • Examined the role of endoplasmic reticulum in spindle positioning.

Main Results:

  • Meiosis I chromosome migration is a biphasic process driven by actin nucleation.
  • Formin 2 (Fmn2) initiates slow, undirected migration by nucleating actin on endoplasmic reticulum.
  • Arp2/3 complex drives fast, directed migration via actin-mediated cytoplasmic streaming upon cortical proximity.

Conclusions:

  • Mouse oocyte symmetry breaking involves Fmn2-mediated spindle perturbation and Arp2/3-driven cytoplasmic streaming.
  • A positive feedback loop between chromosome signaling, Arp2/3 activation, and cytoplasmic streaming ensures directed chromosome transport.

More Related Videos

Capturing Cytoskeleton-Based Agitation of the Mouse Oocyte Nucleus Across Spatial Scales05:43

Capturing Cytoskeleton-Based Agitation of the Mouse Oocyte Nucleus Across Spatial Scales

Published on: January 12, 2024

Related Concept Videos

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...
Meiosis II02:02

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
Meiosis II01:57

Meiosis II

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 chromosomes—one from each homologous initial pair. Importantly, each chromosome in these cells is composed of two joined copies, and when these cells enter meiosis II, the goal is to separate such sister chromatids using the same microtubule-based network employed in other division processes. The result of meiosis II is two haploid cells, each containing...
Meiosis II02:02

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
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...