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Cell. 2007 Aug 10;130(3):484-98.

Self-organization of MTOCs replaces centrosome function during acentrosomal spindle assembly in live mouse oocytes.

Author information

1
Gene Expression Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.

Abstract

Chromosome segregation in mammalian oocytes is driven by a microtubule spindle lacking centrosomes. Here, we analyze centrosome-independent spindle assembly by quantitative high-resolution confocal imaging in live maturing mouse oocytes. We show that spindle assembly proceeds by the self-organization of over 80 microtubule organizing centers (MTOCs) that form de novo from a cytoplasmic microtubule network in prophase and that functionally replace centrosomes. Initially distributed throughout the ooplasm, MTOCs congress at the center of the oocyte, where they contribute to a massive, Ran-dependent increase of the number of microtubules after nuclear envelope breakdown and to the individualization of clustered chromosomes. Through progressive MTOC clustering and activation of kinesin-5, the multipolar MTOC aggregate self-organizes into a bipolar intermediate, which then elongates and thereby establishes chromosome biorientation. Finally, a stable barrel-shaped acentrosomal metaphase spindle with oscillating chromosomes and astral-like microtubules forms that surprisingly exhibits key properties of a centrosomal spindle.

PMID:
17693257
DOI:
10.1016/j.cell.2007.06.025
[Indexed for MEDLINE]
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