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Nat Commun. 2015 Jul 6;6:7217. doi: 10.1038/ncomms8217.

A three-step MTOC fragmentation mechanism facilitates bipolar spindle assembly in mouse oocytes.

Author information

1
Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

Abstract

Assembly of a bipolar microtubule spindle is essential for accurate chromosome segregation. In somatic cells, spindle bipolarity is determined by the presence of exactly two centrosomes. Remarkably, mammalian oocytes do not contain canonical centrosomes. This study reveals that mouse oocytes assemble a bipolar spindle by fragmenting multiple acentriolar microtubule-organizing centres (MTOCs) into a high number of small MTOCs to be able to then regroup and merge them into two equal spindle poles. We show that MTOCs are fragmented in a three-step process. First, PLK1 triggers a decondensation of the MTOC structure. Second, BicD2-anchored dynein stretches the MTOCs into fragmented ribbons along the nuclear envelope. Third, KIF11 further fragments the MTOCs following nuclear envelope breakdown so that they can be evenly distributed towards the two spindle poles. Failure to fragment MTOCs leads to defects in spindle assembly, which delay chromosome individualization and congression, putting the oocyte at risk of aneuploidy.

PMID:
26147444
PMCID:
PMC4501430
DOI:
10.1038/ncomms8217
[Indexed for MEDLINE]
Free PMC Article

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