Oviduct specific glycoprotein 1 (OVGP1) also known as pOSP, MUC-9, sOP92, EAP, EGP and OGP, is produced by non-ciliated oviductal epithelium in many mammalian species. After its secretion to the oviductal fluid OVGP1 participates in the final gamete maturation, sperm capacitation, fertilization and supports early embryonic development. Secretion and expression of OVGP1 is regulated by steroid hormones and depends on the oestrus cycle. Molecular analysis of OVGP1 indicated that it is highly conserved at both amino acid and nucleotide levels.

Maturing vertebrate oocytes become arrested in metaphase of the second meiotic division. These oocytes are ovulated, and then can be activated by sperm or parthenogenetic stimulus. Metaphase arrest is mediated by the cytostatic activity – CSF, that prevents the inactivation of the major M-phase regulator i.e. CDK1-cyclin B kinase. CSF inactivation seems to be necessary for the completion of the second meiotic division and the initiation of the embryonic development. Analysis of amphibian oocyte maturation led to the discovery of factors crucial for the CSF activation.