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Mos limits the number of meiotic divisions in urochordate eggs

Lookup NU author(s): Dr Mark Levasseur


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Mos kinase is a universal mediator of oocyte meiotic maturation and is produced during oogenesis and destroyed after fertilization. The hallmark of maternal meiosis is that two successive M phases (meiosis I and II) drive two rounds of asymmetric cell division (ACD). However, how the egg limits the number of meioses to just two, thereby preventing gross aneuploidy, is poorly characterized. Here, in urochordate eggs, we show that loss of Mos/MAPK activity is necessary to prevent entry into meiosis III. Remarkably, maintaining the Mos/MAPK pathway active after fertilization at near physiological levels induces additional rounds of meiotic M phase (meiosis III, IV and V). During these additional rounds of meiosis, the spindle is positioned asymmetrically resulting in further rounds of ACD. In addition, inhibiting meiotic exit with Mos prevents pronuclear formation, cyclin A accumulation and maintains sperm-triggered Ca2+ oscillations, all of which are hallmarks of the meiotic cell cycle in ascidians. It will be interesting to determine whether Mos availability in mammals can also control the number of meioses as it does in the urochordates. Our results demonstrate the power of urochordate eggs as a model to dissect the egg-to-embryo transition.

Publication metadata

Author(s): Dumollard R, Levasseur M, Hebras C, Huitorel P, Carroll M, Chambon JP, McDougall A

Publication type: Article

Publication status: Published

Journal: Development

Year: 2011

Volume: 138

Issue: 5

Pages: 885-895

Print publication date: 01/03/2011

ISSN (print): 0950-1991

ISSN (electronic): 1477-9129

Publisher: The Company of Biologists Ltd.


DOI: 10.1242/dev.057133


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