Kyozuka K, Osanai K
Asamushi Marine Biological Station, Tohoku University, Aomori, Japan.
Zygote. 1994 May;2(2):103-9. doi: 10.1017/s0967199400001854.
During fertilisation in starfish oocytes, the fertilisation cone develops temporarily beneath the penetrating sperm. The role of the fertilisation cone in sperm incorporation in the starfish Asterias amurensis was examined using cytochalasin B (CB). CB (2 microM) allowed sperm acrosomal process-egg plasma membrane fusion and egg activation, but inhibited the development of the fertilisation cone containing actin microfilaments. When sperm were added to intact oocytes (with the jelly coat and vitelline coat) in seawater containing CB, the sperm head did not penetrate the fertilisation membrane. Although the acrosomal process fused with egg plasma membrane, the sperm head remained outside the fertilisation membrane. On the other hand, denuded oocytes without the jelly coat and vitelline coat allowed sperm penetration even in the presence of 2 microM CB. Electron microscopy revealed that sperm organelles, including the acrosomal process, nucleus, mitochondrion and tail, were incorporated into the slightly electron-dense cytoplasm, which was similar to the cytoplasm of the fertilisation cone. These results show that the development of the fertilisation cone/actin filament complex is not essential for incorporation of the sperm, since incorporation can occur in denuded oocytes. However, the cone is required for fertilisation of intact oocytes, suggesting that this actin-filament-containing structure is necessary for getting the sperm through the outer egg coats.
在海星卵母细胞受精过程中，受精锥在穿透卵子的精子下方暂时形成。使用细胞松弛素B（CB）研究了受精锥在海星多棘海盘车精子纳入过程中的作用。CB（2微摩尔）可使精子顶体突起与卵质膜融合并激活卵子，但会抑制含有肌动蛋白微丝的受精锥的形成。当在含有CB的海水中将精子添加到完整的卵母细胞（带有卵胶膜和卵黄膜）时，精子头部无法穿透受精膜。尽管顶体突起与卵质膜融合，但精子头部仍留在受精膜外。另一方面，去除了卵胶膜和卵黄膜的裸卵即使在存在2微摩尔CB的情况下也能使精子穿透。电子显微镜观察显示，包括顶体突起、细胞核、线粒体和尾部在内的精子细胞器被纳入了电子密度略高的细胞质中，这与受精锥的细胞质相似。这些结果表明，受精锥/肌动蛋白丝复合体的形成对于精子的纳入并非必不可少，因为在裸卵中也能发生精子纳入。然而，受精锥对于完整卵母细胞的受精是必需的，这表明这种含有肌动蛋白丝的结构对于使精子穿过卵子的外层包膜是必要的。
