During oocyte maturation, polar body extrusion results from two asymmetric meiotic cell divisions that depend on the chromosome–spindle complex migrating from the oocyte centre to a subcortical location. Li and colleagues report that this migration occurs in two phases during meiosis I. The first phase was slow and dependent on formin 2 (FMN2). FMN2 colocalized with endoplasmic reticulum structures that surround the spindle and promoted local F-actin nucleation, which pushed the chromosome–spindle complex away from the centre. The second phase was rapid, driven by cytoplasmic streaming and initiated upon activation of a cortical actin-related protein 2/3 (ARP2/3) complex as chromosomes approached the cortex.
ORIGINAL RESEARCH PAPER
Yi, K. et al. Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes. J. Cell Biol. 200, 567–576 (2013)
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Baumann, K. A biphasic push breaks symmetry. Nat Rev Mol Cell Biol 14, 195 (2013). https://doi.org/10.1038/nrm3555
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DOI: https://doi.org/10.1038/nrm3555