Duan Xing, Liu Jun, Zhu Cheng-Cheng, Wang Qiao-Chu, Cui Xiang-Shun, Kim Nam-Hyung, Xiong Bo, Sun Shao-Chen
a College of Animal Science and Technology, Nanjing Agricultural University , Nanjing , China.
b Department of Animal Sciences , Chungbuk National University , Cheongju , Korea.
Cell Cycle. 2016;15(3):471-7. doi: 10.1080/15384101.2015.1128590. Epub 2015 Dec 23.
During oocyte meiosis, the bipolar spindle forms in the central cytoplasm and then migrates to the cortex. Subsequently, the oocyte extrudes the polar body through two successive asymmetric divisions, which are regulated primarily by actin filaments. Myosin light chain2 (MLC2) phosphorylation plays pivotal roles in smooth muscle contraction, stress fiber formation, cell motility and cytokinesis. However, whether MLC2 phosphorylation participates in the oocyte polarization and asymmetric division has not been clarified. The present study investigated the expression and functions of MLC2 during mouse oocyte meiosis. Our result showed that p-MLC2 was localized in the oocyte cortex, with a thickened cap above the chromosomes. Meanwhile, p-MLC2 was also localized in the poles of spindle. Disruption of MLC2 activity by MLC2 knock down (KD) caused the failure of polar body extrusion. Immunofluorescent staining showed that a large proportion of oocytes arrested in telophase stage and failed to undergo cytokinesis after culturing for 12 hours. In the meantime, actin filament staining at oocyte membrane and cytoplasm were reduced in MLC2 KD oocytes. Finally, we found that the phosphorylation of MLC2 protein levels was decreased after disruption of RhoA activity. Above all, our data indicated that the RhoA-mediated MLC2 regulates the actin organization for cytokinesis during mouse oocyte maturation.
在卵母细胞减数分裂过程中，双极纺锤体在中央细胞质中形成，然后迁移至皮质。随后，卵母细胞通过两次连续的不对称分裂排出极体，这主要受肌动蛋白丝调控。肌球蛋白轻链2（MLC2）磷酸化在平滑肌收缩、应力纤维形成、细胞运动和胞质分裂中起关键作用。然而，MLC2磷酸化是否参与卵母细胞极化和不对称分裂尚未明确。本研究调查了MLC2在小鼠卵母细胞减数分裂过程中的表达及功能。我们的结果显示，p-MLC2定位于卵母细胞皮质，在染色体上方有增厚的帽状结构。同时，p-MLC2也定位于纺锤体两极。通过敲低（KD）MLC2破坏其活性会导致极体排出失败。免疫荧光染色显示，培养12小时后，大部分卵母细胞停滞在末期，无法进行胞质分裂。与此同时，MLC2 KD卵母细胞的卵母细胞膜和细胞质中的肌动蛋白丝染色减少。最后，我们发现RhoA活性被破坏后，MLC2蛋白水平的磷酸化降低。综上所述，我们的数据表明，RhoA介导的MLC2在小鼠卵母细胞成熟过程中调节胞质分裂的肌动蛋白组织。
