Functional analysis of oocyte-specific gene, c-1, which express during meiosis

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In the present study, we report the protein expression and localization of a novel gene (named Oogenesin) in mouse oocytes and embryos. The gene was first isolated based on its elevated expression in 2-cell embryos developed without oviductal tissue, in which embryos cannot develop beyond the 2-cell stage. Molecular cloning of a near full-length cDNA revealed that the novel gene encodes a protein composed of 398 amino acids corresponding to a predicted molecular mass of 46 kDa. A remarkable characteristic of the gene is that it contains a leucine zipper at positions 203-224 and a leucine-rich domain at positions 137-326. In situ hybridization using an RNA probe in sections of the adult ovary resulted in distinct signals in the oocyte of all stages of follicles. Expression analysis of a novel cDNA isolated from various stages of preimplantation embryos revealed that Oogenesin expression abruptly decreased after the 2-cell stage and disappeared after the 4-cell stage.A western blot analy … More sis using an affinity-purified rabbit polyclonal antibody raised against a synthetic peptide revealed that the molecular size of OOGENESIN protein is approximately 46 kDa, which is consistent with the size predicted on the basis of the Oogenesin cDNA. OOGENESIN is expressed predominantly in oocytes and 1-to 4-cell stage embryos, whereas it is expressed only weakly in morula/blastocyst stage embryos. Increasing expression was observed from oocytes to the 1-cell stage and the expression decreased toward the 4-cell stage. Immunohistochemistry detected strong signals in oocytes of secondary and antral follicles, and weak signals in oocytes of primordial and primary follicles. All signals were detected in the cytoplasm of follicular oocytes. However, immunohistochemical analysis of ovulated oocytes and preimplantation embryos revealed that the protein localized in the nuclei at late 1-cell and early 2-cell stage. These results together with the unique structure of the protein suggest that Oogenesin has important roles in the transcriptional activation, especially in zygotic gene activation of mouse embryos as a novel maternal effect gene. Less