The expression and localization of zona pellucida glycoproteins and mRNA in cynomolgus monkeys (Macaca fascicularis).

The zona pellucida (ZP) is an extracellular matrix composed of multiple glycoproteins that surrounds all mammalian oocytes. Analysis of the genes encoding the ZP proteins indicates that there are three classes ZPA (largest), ZPB (intermediate) and ZPC (smallest). Polyclonal antibodies developed against recombinant proteins of human and pig ZP have been used to identify immunohistochemically the components of the ZP of cynomolgus monkeys during the course of follicular development. Digoxigenin-labelled cDNA probes specific for the mRNA encoding ZPA, ZPB or ZPC were used to probe sections of cynomolgus monkey ovaries by in situ hybridization. mRNA encoding ZPA was identified in growing follicles at all stages and was seen in the granulosa cells of mature preovulatory follicles. ZPB protein and mRNA encoding ZPB were present in oocytes in secondary follicles and to a lesser extent in tertiary follicles, but were not found in primordial, primary or antral follicles or granulosa cells. ZPC protein and mRNA encoding ZPC were present in oocytes at all stages of folliculogenesis. These results suggest that each component of the ZP is produced and secreted at specific stages of folliculogenesis and that granulosa cells may be contributing to the synthesis of ZPA and ZPC.