title: Overexpression of SETβ, a protein localizing to centromeres, causes precocious separation of chromatids during the first meiosis of mouse oocytes.
abstract: Chromosome segregation in mammalian oocyte meiosis is an error-prone process, and any mistake in this process may result in aneuploidy, which is the main cause of infertility, abortion and many genetic diseases. It is now well known that shugoshin and protein phosphatase 2A (PP2A) play important roles in the protection of centromeric cohesion during the first meiosis. PP2A can antagonize the phosphorylation of rec8, a member of the cohesin complex, at the centromeres and thus prevent cleavage of rec8 and so maintain the cohesion of chromatids. SETβ is a protein that physically interacts with shugoshin and inhibits PP2A activity. We thus hypothesized that SETβ might regulate cohesion protection and chromosome segregation during oocyte meiotic maturation. Here we report for the first time the expression, subcellular localization and functions of SETβ during mouse oocyte meiosis. Immunoblotting analysis showed that the expression level of SETβ was stable from the germinal vesicle stage to the MII stage of oocyte meiosis. Immunofluorescence analysis showed SETβ accumulation in the nucleus at the germinal vesicle stage, whereas it was targeted mainly to the inner centromere area and faintly localized to the interchromatid axes from germinal vesicle breakdown to MI stages. At the MII stage, SETβ still localized to the inner centromere area, but could relocalize to kinetochores in a process perhaps dependent on the tension on the centromeres. SETβ partly colocalized with PP2A at the inner centromere area. Overexpression of SETβ in mouse oocytes caused precocious separation of sister chromatids, but depletion of SETβ by RNAi showed little effects on the meiotic maturation process. Taken together, our results suggest that SETβ, even though it localizes to centromeres, might not be essential for chromosome separation during mouse oocyte meiotic maturation, although its forced overexpression causes premature chromatid separation.
authors: State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
authors: Shu-Tao
authors: ST
authors: Qi
authors: Zhen-Bo
authors: ZB
authors: Wang
authors: Ying-Chun
authors: YC
authors: Ouyang
authors: Qing-Hua
authors: QH
authors: Zhang
authors: Meng-Wen
authors: MW
authors: Hu
authors: Xin
authors: X
authors: Huang
authors: Zhaojia
authors: Z
authors: Ge
authors: Lei
authors: L
authors: Guo
authors: Ya-Peng
authors: YP
authors: Wang
authors: Yi
authors: Y
authors: Hou
authors: Heide
authors: H
authors: Schatten
authors: Qing-Yuan
authors: QY
authors: Sun
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002503:Centromere / Q000378:metabolism*; D002842:Chromatids / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005260:Female; D005455:Fluorescent Antibody Technique; D056488:Histone Chaperones; D008540:Meiosis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D015513:Oncogene Proteins; C557500:SET protein, mouse; D054648:Protein Phosphatase 2
keywords: Centromere; Chromosome separation; Cohesion; Meiosis; Mouse oocyte; PP2A; SETβ