Hedrick Jerry L
Department of Animal Science, University of California, Davis, CA 95616, USA.
Soc Reprod Fertil Suppl. 2007;63:409-19.
Fertilization is a critically important event to the creation of a new individual organism and to the propagation of a species. Evolutionarily conserved cellular and molecular mechanisms exist to modify the glycoproteins composing the egg extracellular matrix at fertilization. These matrix modifications regulate the cellular interactions of sperm and egg, maintain the diploid state of the nucleus after successful union of the two gametes (block to polyspermy) and control the environment for the developing embryo. Only recently have mammals been studied regarding extracellular matrix block to polyspermy mechanisms compared to the long term investigations of the same in sea urchins, fish and amphibians - knowledge of evolutionary conserved mechanisms in these animal groups can be used to predict the existence of mechanisms in mammals. Experimental evidence exists for the conservation of proteolytic, glycolytic, cross linking, conformational and binding mechanisms for establishing extracellular matrix blocks to polyspermy at fertilization. Analogous to a binding mechanism in anurans, a lectin-ligand binding mechanism for establishing an extracellular matrix block to polyspermy in mammalian eggs has been discovered. This binding mechanism involves the exocytotic release of a cortical granule lectin in the sperm-induced egg cortical reaction, diffusion and binding of the lectin to its ligand associated with the zona pellucida, and prevention of sperm-zona pellucida binding by the lectin-ligand reaction, thereby resulting in a block to polyspermy at fertilization. The glycoproteins involved in the lectin-ligand polyspermy block can potentially be used as targets for contraception.
受精对于新个体生物的产生以及物种的繁衍来说是极其重要的事件。进化上保守的细胞和分子机制在受精时存在，用于修饰构成卵外基质的糖蛋白。这些基质修饰调节精子与卵子的细胞相互作用，在两个配子成功结合后维持细胞核的二倍体状态（阻止多精受精），并为发育中的胚胎控制环境。与对海胆、鱼类和两栖动物进行的长期研究相比，直到最近才对哺乳动物的细胞外基质阻止多精受精机制进行研究——这些动物群体中进化保守机制的知识可用于预测哺乳动物中机制的存在。存在实验证据表明，在受精时建立细胞外基质阻止多精受精的蛋白水解、糖酵解、交联、构象和结合机制具有保守性。类似于无尾两栖类动物中的一种结合机制，已经发现了一种凝集素 - 配体结合机制，用于在哺乳动物卵子中建立细胞外基质阻止多精受精。这种结合机制涉及在精子诱导的卵皮质反应中皮质颗粒凝集素的胞吐释放、凝集素向与透明带相关的配体的扩散和结合，以及通过凝集素 - 配体反应阻止精子与透明带的结合，从而在受精时导致阻止多精受精。参与凝集素 - 配体阻止多精受精的糖蛋白有可能用作避孕靶点。
