Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Education Ministry of China, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China.
Mol Reprod Dev. 2013 Jun;80(6):474-87. doi: 10.1002/mrd.22185. Epub 2013 May 28.
Bora is the binding partner of Aurora A, which is required for its activation and phosphorylation of Polo like kinase 1 (Plk1), and is involved in the spindle assembly and progress of the cell cycle during mitosis. In this study, we examined the expression, localization, and function of Bora during mouse oocyte meiosis. The expression level of Bora was increased during oocyte meiotic maturation, with an elevated level at metaphase. Immunofluorescence analysis showed that Bora was concentrated as a dot shortly after germinal vesicle breakdown (GVBD), associating first with the surrounding chromosomes and then with the spindle throughout oocyte meiotic maturation. Further experiments confirmed that Bora co-localized with α-tubulin at prometaphase/metaphase, but dissociated from α-tubulin at anaphase/telophase. In metaphase-II-arrested oocytes, Bora was evenly distributed in the cytoplasm after treatment with a microtubule-depolymerizing agent, or recruited to the spindle after treatment with a microtubule-polymerizing agent, indicating that Bora was physically connected to the meiotic spindle and α-tubulin at metaphase. Furthermore, inhibition or depletion of Bora by either anti-Bora antibody or Bora siRNA microinjection significantly reduced the rates of GVBD and inhibited first polar body extrusion; caused morphologically defective spindles and misaligned chromosomes; arrested maturing oocytes at prometaphase/metaphase-I stage, or left oocytes and their first polar bodies with severely misaligned chromosomes and defective spindles; and/or caused the disappearance of Aurora A and Plk1 at the spindle. These results indicated that Bora acts as a critical regulator of Aurora A and Plk1, and is involved in microtubule organization during oocyte meiosis.
博来是 Aurora A 的结合伴侣，对于 Aurora A 的激活和磷酸化 Polo 样激酶 1（Plk1）是必需的，并且在有丝分裂过程中参与纺锤体的组装和细胞周期的进展。在这项研究中，我们检查了 Bora 在小鼠卵母细胞减数分裂过程中的表达、定位和功能。Bora 的表达水平在卵母细胞减数成熟过程中增加，在中期达到高峰。免疫荧光分析显示，Bora 在生发泡破裂（GVBD）后不久聚集为一个点，首先与周围的染色体结合，然后在整个卵母细胞减数成熟过程中与纺锤体结合。进一步的实验证实，Bora 在前期/中期与α-微管蛋白共定位，但在后期/末期与α-微管蛋白解离。在中期 II 阻滞的卵母细胞中，用微管解聚剂处理后，Bora 在细胞质中均匀分布，或在用微管聚合剂处理后募集到纺锤体上，表明 Bora 在中期与减数纺锤体和α-微管蛋白物理连接。此外，用抗 Bora 抗体或 Bora siRNA 微注射抑制或耗尽 Bora 会显著降低 GVBD 率并抑制第一极体排出；导致形态缺陷的纺锤体和染色体排列不齐；将成熟卵母细胞阻滞在前期/中期 I 期，或使卵母细胞及其第一极体带有严重排列不齐的染色体和缺陷的纺锤体；和/或导致纺锤体上 Aurora A 和 Plk1 的消失。这些结果表明，Bora 作为 Aurora A 和 Plk1 的关键调节因子，参与卵母细胞减数分裂过程中的微管组织。
