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BOR - Papers in Press, published online ahead of print July 2, 2008.
Biol Reprod 2008, 10.1095/biolreprod.108.069641
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BIOLOGY OF REPRODUCTION 79, 718–726 (2008)
DOI: 10.1095/biolreprod.108.069641
© 2008 by the Society for the Study of Reproduction, Inc.

BRCA1 Is Required for Meiotic Spindle Assembly and Spindle Assembly Checkpoint Activation in Mouse Oocytes1

Bo Xiong 3 4, Sen Li 3 4, Jun-Shu Ai 3 4, Shen Yin 3 4, Ying-Chun OuYang 3, Shao-Chen Sun 3 5, Da-Yuan Chen 3, and Qing-Yuan Sun 2 3

State Key Laboratory of Reproductive Biology,3 Institute of Zoology; and Graduate School,4 Chinese Academy of Sciences, 100080 Beijing, China Animal Reproduction Institute,5 Gugangxi Key Laboratory of Subtropical Bioresource Conservation and Utilization, Guangxi University, 530005 Nanning, China

ABSTRACT

BRCA1 as a tumor suppressor has been widely investigated in mitosis, but its functions in meiosis are unclear. In the present study, we examined the expression, localization, and function of BRCA1 during mouse oocyte meiotic maturation. We found that expression level of BRCA1 was increased progressively from germinal vesicle to metaphase I stage, and then remained stable until metaphase II stage. Immunofluorescent analysis showed that BRCA1 was localized to the spindle poles at metaphase I and metaphase II stages, colocalizing with centrosomal protein gamma-tubulin. Taxol treatment resulted in the presence of BRCA1 onto the spindle microtubule fibers, whereas nocodazole treatment induced the localization of BRCA1 onto the chromosomes. Depletion of BRCA1 by both antibody injection and siRNA injection caused severely impaired spindles and misaligned chromosomes. Furthermore, BRCA1-depleted oocytes could not arrest at the metaphase I in the presence of low-dose nocodazole, suggesting that the spindle checkpoint is defective. Also, in BRCA1-depleted oocytes, gamma-tubulin dissociated from spindle poles and MAD2L1 failed to rebind to the kinetochores when exposed to nocodazole at metaphase I stage. Collectively, these data indicate that BRCA1 regulates not only meiotic spindle assembly, but also spindle assembly checkpoint, implying a link between BRCA1 deficiency and aneuploid embryos.

aneuploid embryo, BRCA1, meiosis, mouse oocyte, spindle assembly, spindle assembly checkpoint

FOOTNOTES

1Supported by the National Basic Research Program of China (2006CB944001, 2006CB504004), National Natural Science Foundation of China (30430530, 30570944), and Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2-YW-R-52).

Correspondence: 2Correspondence: Qing-Yuan Sun, State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China. FAX: 86 10 64807099; e-mail: sunqy{at}ioz.ac.cn






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Copyright © 2008 by the Society for the Study of Reproduction.