Molecular cloning and characterization of a new gene, Oocyte-G1

Oocytes are recognized as a source of regulatory molecules that influence follicular development through an array of actions on granulosa cells. Recently, more and more hormones and signaling molecules were identified during follicular developmental processes; however, the details about their functions are still unclear. During efforts to clone follicular development-related genes, we isolated a cDNA fragment by DDRT-PCR. To obtain cDNA 5'- and 3'-end sequences, we screened a mouse ovarian cDNA library. After screening the library, an open reading frame of 2,994 bp for the new gene (Oocyte-G1), which encodes a 997-residue protein, was cloned. Northern blot analysis revealed the presence of approximately 3.6 kb Oocyte-G1 mRNA in ovary, lung, kidney, testis and brain. Northern analysis of RNA from ovaries in vivo showed that Oocyte-G1 was weakly expressed on day 5 and at a moderate level on day 10. Thereafter, on day 15 or in adults (day 40), there was an increase in expression, followed by a decline in ovaries on day 20 or older (day 120). Furthermore, we studied the Ooctye-G1 protein by using the antiserum against a peptide sequence unique to this gene in Western blotting and immunolocalization. The antiserum recognized a prominent band of approximately 110 kDa in immunoblots and signals were dispersed in oocytes and some cumulus granulosa cells. Our results suggest the potential role of Oocyte-G1 in ovarian follicular development.