Studies on the mechanism of sperm-egg interaction

本研究分析了小鼠卵巢卵母细胞带糖蛋白的精子受体活性，以及单个糖蛋白中的低聚糖。为了确定具有精子结合活性的糖蛋白，我们使用了体外结合试验。测试了失能精子与固定在乳胶珠上的糖蛋白的结合。结果表明，ZP-3糖蛋白与精子的结合能力最强。然而，在测定精子中与ZP-3结合活性的组分时，没有得到阳性结果。假设ZP-3糖蛋白可能具有独特的碳水化合物，反映了其与其他带糖蛋白的功能差异，采用同位素标记的糖蛋白对其进行了凝胶层析比较。所有带状糖蛋白均含有O-和n -低聚糖，但各糖蛋白的碳水化合物含量和O-和n -低聚糖的含量比例不同。n -链碳水化合物具有不被唾液酸酶释放的负电荷，并且含有n -链低聚糖中通常不存在的n -乙酰半乳糖胺。三种糖蛋白在O-和n -低聚糖的凝胶层析上显示出相似的模式，并且在糖蛋白之间没有检测到低聚糖的特征差异。然而，来自两细胞胚胎的ZP-3寡糖与未受精卵的模式发生了改变，这可能反映了两细胞胚胎透明带的功能修饰。对这些在受精过程中发生结构变化的寡糖的进一步研究可能有助于阐明精卵相互作用的机制。

In the present study, we analyzed the sperm receptor activity of the zona glycoproteins from mouse ovarian oocytes, and oligosaccharides in individual glycoproteins. For the determination of the glycoprotein that has the sperm binding activity, we used a in vitro binding assay. Capacitated sperm were tested for the binding to the glycoprotein immobilized on latex beads. The results indicated that ZP-3 glycoprotein had the highest capacity to bind sperm. However, no positive results were obtained in an attempt to determine the sperm components that had the binding activity to ZP-3.Assuming that the ZP-3 glycoprotein might have the unique carbohydrates reflecting its functional difference from the rest of zona glycoproteins, gel chromatographic comparison of the oligosaccharides was made using isotopically labeled glycoproteins. All of the zona glycoproteins contained both O- and N-linked oligosaccharides, although carbohydrate content and ratio of the amount of O- and N-linked oligosaccharides siffered among the glycoproteins. N-linked carbohydrates had negative charge not released by sialidase, and contained N-acetylgalactosamine usally not found in N-linked oligosaccharides. All three glycoproteins showed the similar patterns on gel chromatography of both O- and N-linked oligosaccharides, and no characteristic difference of oligosaccharides has been detected among the glycoproteins. However, ZP-3 oligosaccharides from two-cell embryos gave altered patterns from unfertilized eggs, probably reflecting the functional modification of the zona pellucida in two-cell embryos. Future studies on these oligosaccharides that undergo the structural changes in fertilization could result in the elucidation of the mechanism of sperm-egg interaction.