Zhu Zi-Yu, Chen Da-Yuan, Li Jin-Song, Lian Li, Lei Lei, Han Zhi-Ming, Sun Qing-Yuan
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China.
Biol Reprod. 2003 Mar;68(3):943-6. doi: 10.1095/biolreprod.102.009910.
The completion of meiosis requires the spatial and temporal coordination of cytokinesis and karyokinesis. During meiotic maturation, many events, such as formation, location, and rotation of the meiotic spindle as well as chromosomal movement, polar body extrusion, and pronuclear migration, are dependent on regulation of the cytoskeleton system. To study functions of microfilaments in meiosis, we induced metaphase II (MII) mouse oocytes to resume meiosis by in vitro fertilization or parthenogenetic activation, and we treated such oocytes with cytochalasin B (CB). The changes of the meiotic spindle, as visualized in preparations stained for beta-tubulin and chromatin, were observed by fluorescent confocal microscopy. The meiotic spindle of MII oocytes was observed to be parallel to the plasmalemma. After meiosis had resumed, the spindle rotated to the vertical position so that the second polar body could be extruded into the perivitelline space. When meiosis resumed and oocytes were treated with 10 micro g/ml of CB, the spindle rotation was inhibited. Consequently, the oocyte formed an extra pronucleus instead of extruding a second polar body. These results indicate that spindle rotation is essential for polar body extrusion; it is the microfilaments that play a crucial role in regulating rotation of the meiotic spindle.
减数分裂的完成需要胞质分裂和核分裂在空间和时间上的协调。在减数分裂成熟过程中，许多事件，如减数分裂纺锤体的形成、定位和旋转以及染色体运动、极体排出和原核迁移，都依赖于细胞骨架系统的调节。为了研究微丝在减数分裂中的功能，我们通过体外受精或孤雌激活诱导中期II（MII）小鼠卵母细胞恢复减数分裂，并用细胞松弛素B（CB）处理这些卵母细胞。通过荧光共聚焦显微镜观察在β-微管蛋白和染色质染色的制剂中可视化的减数分裂纺锤体的变化。观察到MII卵母细胞的减数分裂纺锤体与质膜平行。减数分裂恢复后，纺锤体旋转到垂直位置，以便第二极体可以被挤出到卵周间隙中。当减数分裂恢复且卵母细胞用10μg/ml的CB处理时，纺锤体旋转受到抑制。因此，卵母细胞形成了一个额外的原核而不是挤出第二极体。这些结果表明纺锤体旋转对于极体排出至关重要；是微丝在调节减数分裂纺锤体的旋转中起关键作用。
