Mammalian fertilization:the eggs multifunctional zona pellucida

TL;DRAbstract

The zona pellucida (ZP) is a specialized extracellular coat that surrounds the plasma membrane of mammalian eggs. Its presence is essential for successful completion of oogenesis, fertilization and preimplantation development. The ZP is composed of only a few glycoproteins which are organized into long crosslinked fibrils that constitute the extracellular coat. A hallmark of ZP glycoproteins is the presence of a ZP domain, a region of polypeptide responsible for polymerization of the glycoproteins into a network of interconnected fibrils. The mouse egg ZP consists of only three glycoproteins, called ZP1, ZP2, and ZP3, that are synthesized and secreted exclusively by growing oocytes. One of the glycoproteins, ZP3, serves as both a binding partner for sperm and inducer of sperm exocytosis, the acrosome reaction. Female mice lacking ZP3 fail to assemble a ZP around growing oocytes and are completely infertile. Sperm bind to the carboxy-terminal region of ZP3 polypeptide encoded by ZP3 exo

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