title: BRCA1 is required for meiotic spindle assembly and spindle assembly checkpoint activation in mouse oocytes.
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.
authors.affiliation: State Key Laboratory of Reproductive Biology, Chinese Academy of Sciences, 100080 Beijing, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Xiong
authors.forename: Sen
authors.initials: S
authors.lastname: Li
authors.forename: Jun-Shu
authors.initials: JS
authors.lastname: Ai
authors.forename: Shen
authors.initials: S
authors.lastname: Yin
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: Ouyang
authors.forename: Shao-Chen
authors.initials: SC
authors.lastname: Sun
authors.forename: Da-Yuan
authors.initials: DY
authors.lastname: Chen
authors.forename: Qing-Yuan
authors.initials: QY
authors.lastname: Sun
mesh_terms: D000782:Aneuploidy; D000818:Animals; D019313:BRCA1 Protein / Q000378:metabolism / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005260:Female; D064246:Mad2 Proteins; D008540:Meiosis / Q000187:drug effects / Q000502:physiology; D051379:Mice; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009866:Oogenesis / Q000187:drug effects / Q000502:physiology; D017239:Paclitaxel / Q000494:pharmacology; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D014018:Tissue Distribution / Q000187:drug effects; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D064246:Mad2 Proteins; C577698:Mad2l1 protein, mouse; D009687:Nuclear Proteins; D050257:Tubulin Modulators; D017239:Paclitaxel; D015739:Nocodazole