Science of Bioresource Production, The United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima City, Kagoshima 890-0065, Japan.
Theriogenology. 2011 Apr 1;75(6):1146-52. doi: 10.1016/j.theriogenology.2010.11.026. Epub 2011 Jan 8.
The objective was to determine whether N-glycosylation of zona pellucida (ZP) glycoproteins occurred during meiotic maturation of porcine oocytes, and whether this had a role in fertilization. In the first of three experiments, carbohydrate residues in the ZP of in vitro matured porcine oocytes were blocked with various lectins and the influence of such blocking on sperm-ZP interactions was studied. The second experiment used a lectin-binding assay to determine whether the number of GlcNAc residues in ZP was changed by N-glycosylation during in vitro maturation (IVM) of porcine oocytes. The last experiment determined the effects of tunicamycin, a specific N-glycosylation inhibitor, for various intervals during IVM, on sperm-ZP interactions in porcine oocytes. The primary findings were that: 1) N-glycosylation of GlcNAc residues in porcine ZP occurred during the first 24 h of IVM; and 2) such glycosylation was indispensible for sperm-ZP interactions, e.g., number of sperm bound to ZP, acrosome-reacted sperm, sperm penetration rate, and level of polyspermy (P < 0.05). However, blocking N-glycosylation by tunicamycin treatment during IVM did not adversely influence the progression of oocytes to meiotic metaphase II and male pronucleus formation, indicating that this glycosylation was involved only in the initial stages of fertilization. We inferred that the increase in terminal GlcNAc residues in ZP glycoprotein through new N-glycosylation during the first 24 h of meiotic maturation played a critical role in porcine ZP acquiring the capacity to accept sperm.
目的是确定猪卵母细胞减数分裂成熟过程中是否发生了透明带（ZP）糖蛋白的 N-糖基化，以及这种糖基化是否在受精过程中起作用。在三个实验中的第一个实验中，用各种凝集素阻断体外成熟猪卵母细胞 ZP 中的碳水化合物残基，并研究这种阻断对精子-ZP 相互作用的影响。第二个实验使用凝集素结合测定法来确定在猪卵母细胞体外成熟（IVM）过程中 N-糖基化是否改变了 ZP 中的 GlcNAc 残基数量。最后一个实验确定了在 IVM 过程中不同时间使用特异性 N-糖基化抑制剂衣霉素对猪卵母细胞中精子-ZP 相互作用的影响。主要发现如下：1）猪 ZP 中的 GlcNAc 残基的 N-糖基化发生在 IVM 的前 24 小时内；2）这种糖基化对于精子-ZP 相互作用是必不可少的，例如，附着在 ZP 上的精子数量、顶体反应的精子、精子穿透率和多精受精水平（P <0.05）。然而，在 IVM 期间用衣霉素处理阻断 N-糖基化并不会对卵母细胞向减数分裂中期 II 和雄性原核形成的进展产生不利影响，这表明这种糖基化仅参与受精的初始阶段。我们推断，在减数分裂成熟的最初 24 小时内，通过新的 N-糖基化使 ZP 糖蛋白末端的 GlcNAc 残基增加，这对于猪 ZP 获得接受精子的能力起着关键作用。
