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FZR1, an activator of the anaphase-promoting complex/cyclosome (APC/C), is recognized for its roles in the mitotic cell cycle. To examine its meiotic function in females we generated an oocyte-specific knockout of the Fzr1 gene (Fzr1(Delta/Delta)). The total number of fully grown oocytes enclosed in cumulus complexes was 35-40% lower in oocytes from Fzr1(Delta/Delta). mice and there was a commensurate rise in denuded, meiotically advanced and/or fragmented oocytes. The ability of Fzr1(Delta/Delta) oocytes to remain prophase I/germinal vesicle (GV) arrested in vitro was also compromised, despite the addition of the phosphodiesterase milrinone. Meiotic competency of smaller diameter oocytes was also accelerated by Fzr1 loss. Cyclin B1 levels were elevated similar to 5-fold in Fzr1(Delta/Delta) oocytes, whereas securin and CDC25B, two other APC/C-FZR1 substrates, were unchanged. Cyclin B1 overexpression can mimic the effects of Fzr1 loss on GV arrest and here we show that cyclin B1 knockdown in Fzr1(Delta/Delta) oocytes affects the timing of meiotic resumption. Therefore, the effects of Fzr1 loss are mediated, at least in part, by raised cyclin B1. Thus, APC/C-FZR1 activity is required to repress cyclin B1 levels in oocytes during prophase I arrest in the ovary, thereby maintaining meiotic quiescence until hormonal cues trigger resumption.
Author(s): Holt JE, Tran SMT, Stewart JL, Minahan K, Garcia-Higuera I, Moreno S, Jones KT
Publication type: Article
Publication status: Published
Journal: Development
Year: 2011
Volume: 138
Issue: 5
Pages: 905-913
Print publication date: 01/03/2011
ISSN (print): 0950-1991
ISSN (electronic): 1477-9129
Publisher: The Company of Biologists Ltd.
URL: http://dx.doi.org/10.1242/dev.059022
DOI: 10.1242/dev.059022
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