Xiu-Lan Zhu

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (3)9.13 Total impact

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    ABSTRACT: Checkpoint kinase 1 (Chk1) plays key roles in all currently defined cell cycle checkpoints, but its functions in mouse oocyte meiosis remain unclear. In this study, we report the expression, localization and functions of Chk1 in mouse oocyte meiosis. Chk1 was expressed from germinal vesicle (GV) to metaphase II (MII) stages and localized to the spindle from pro-metaphase I (pro-MI) to MII stages in mouse oocytes. Chk1 depletion facilitated the G 2/M transition while Chk1 overexpression inhibited the G 2/M transition as indicated by germinal vesicle breakdown (GVBD), through regulation of Cdh1 and Cyclin B1. Chk1 depletion did not affect meiotic cell cycle progression after GVBD, but its overexpression after GVBD activated the spindle assembly checkpoint and prevented homologous chromosome segregation, thus arresting oocytes at pro-MI or metaphase I (MI) stages. These results suggest that Chk1 is indispensable for prophase I arrest and functions in G 2/M checkpoint regulation in meiotic oocytes. Moreover, Chk1 overexpression affects meiotic spindle assembly checkpoint regulation and thus chromosome segregation.
    No preview · Article · May 2012 · Cell cycle (Georgetown, Tex.)
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    ABSTRACT: Synaptotagmin1, a calcium sensor for exocytosis, forms the 7S complex, or so-called SNARE protein complex, together with SNAP -25, syntaxin and synaptobrevin to mediate docking and fusion of synaptic vesicles to the plasma membrane of the nerve terminal. Here, we identified the unique localization, expression and function of Syt1 during mouse oocyte meiotic maturation by using confocal microscopy, western blotting, Morpholino-based knockdown and time-lapse live cell imaging. We showed that Syt1 expression was gradually increased during oocyte maturation. Syt1 was localized at the oocyte cortex from GV to MII stages and at the spindle poles in MI and MII phases, with one third of a signal-free zone at the oocyte cortex, where the chromosomes are located, which is similar to the distribution pattern of CGs from the pro-MI to MII stages. Knockdown of Syt1 resulted in pro-MI/MI arrest and PB1 extrusion decrease, with severely disrupted spindles and misaligned chromosomes. Knockdown of Syt1 also caused abnormal localization of γ-tubulin, which became redistributed into the cytoplasm. Chromosome spreading showed failure of homologous chromosome segregation. The spindle assembly checkpoint protein Bub3 was detected at the kinetochores even after 10 h of oocyte culture. Live cell imaging analysis revealed that knockdown of Syt1 resulted in abnormal spindles with various morphologies and chromosomes arrested at the pro-MI/MI stage. Defective spindles failed to support chromosome alignment along microtubules, which led to repetitive unsuccessful metaphase-anaphase transitions and failure of PB1 extrusion after extended culture. Taken together, we suggest that Syt1 may act as a MTOC-associated protein to play important roles in mouse oocyte spindle organization/stability, and that it is indispensable for the metaphase-anaphase transition to promote mouse oocyte meiotic maturation.
    Preview · Article · Feb 2012 · Cell cycle (Georgetown, Tex.)

  • No preview · Article · Jan 2012 · Medical Journal of Chinese People's Liberation Army

Publication Stats

8 Citations
9.13 Total Impact Points


  • 2012
    • Chinese Academy of Sciences
      • State Key Laboratory of Reproductive Biology
      Peping, Beijing, China