Localization and synthesis of zona pellucida proteins in the marmoset monkey (Callithrix jacchus) ovary

In most species, the zona pellucida (ZP), an extracellular matrix surrounding the mammalian oocyte, is composed of three glycoproteins: ZPA, ZPB and ZPC. Based mainly on results with mice, the site of zona pellucida biosynthesis has been suggested to be exclusively in the oocyte cytoplasm. However, evidence is accumulating that among various species cumulus/granulosa cells may be involved. Because knowledge of ZP biosynthesis in primates is lacking, we used the common marmoset (Callithrix jacchus) to acquire information about the localization and the site of synthesis of ZP proteins in this species. Using antibodies against synthetic ZPA and ZPC peptides, immunoreactivity was found in the marmoset ZP and in surrounding cumulus cells. Interestingly, the amounts of ZPA and ZPC proteins expressed appeared to differ depending on the stage of folliculogenesis. RT–PCR analysis of mRNA from marmoset oocytes and from oocyte-free follicle cells revealed expression of ZPA, ZPB and ZPC in oocytes and in follicle cells of different stages of marmoset monkey folliculogenesis. Our data suggest that the biosynthesis of marmoset ZPA, ZPB and ZPC proteins takes place both in oocytes and in follicle cells of different follicle stages, although the abundance of ZP glycoproteins may differ depending on the individual ZP protein.