Oog1, an oocyte-specific protein, interacts with Ras and Ras-signaling proteins during early embryogenesis. Tsukamoto S et al. We previously identified an oocyte-specific gene, Oogenesin 1 (Oog1), that encodes 326 amino acids containing a leucine zipper structure and a leucine-rich repeat. In the present study, to identify the interacting proteins of Oog1, we performed a yeast two-hybrid screening using a GV-oocyte cDNA library and found that Ral guanine nucleotide dissociation stimulator (RalGDS) is the binding partner of Oog1. Coimmunoprecipitation assay confirmed the interaction between Oog1 and RalGDS proteins. Colocalization experiments provide the evidence that the nuclear localization of RalGDS depends on the expression of Oog1. Interestingly, RalGDS protein localized in the nucleus rather than the cytoplasm between late 1-cell and early 2-cell stages, the time when Oog1 localizes in the nucleus. We also examined the interaction between Oog1 and Ras by GST pull-down assay and revealed that Oog1 interacts with Ras in a GTP-dependent manner. These findings suggest a role of Oog1 as a Ras-binding protein.
General function
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Cellular localization
Nuclear
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Ovarian function
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Oocyte-specific gene Oog1 suppresses the expression of spermatogenesis-specific genes in oocytes. Honda S et al. (2018) Oog1, an oocyte-specific gene that encodes a protein of 425 amino acids, is present in five copies on mouse chromosomes 4 and 12. In mouse oocytes, Oog1 mRNA expression begins at embryonic day 15.5 and almost disappears by the late two-cell stage. Meanwhile, OOG1 protein is detectable in oocytes in ovarian cysts and disappears by the four-cell stage; the protein is transported to the nucleus in late one-cell to early two-cell stage embryos. In this study, we examined the role of Oog1 during oogenesis in mice. Oog1 RNAi-transgenic mice were generated by expressing double-stranded hairpin Oog1 RNA, which is processed into siRNAs targeting Oog1 mRNA. Quantitative RT-PCR revealed that the amount of Oog1 mRNA was dramatically reduced in oocytes obtained from Oog1-knockdown mice, whereas the abundance of spermatogenesis-associated transcripts (Klhl10, Tekt2, Tdrd6, and Tnp2) was increased in Oog1 knockdown ovaries. Tdrd6 is involved in the formation of the chromatoid body, Tnp2 contributes to the formation of sperm heads, Tekt2 is required for the formation of ciliary and flagellar microtubules, and Klhl10 plays a key role in the elongated sperm differentiation. These results indicate that Oog1 down-regulates the expression of spermatogenesis-associated genes in female germ cells, allowing them to develop normally into oocytes.//////////////////
Oogenesis specific genes (Nobox, Oct4, Bmp15, Gdf9, Oogenesin1 and Oogenesin2) are differentially expressed during natural and gonadotropin-induced mouse follicular development. Monti M et al. (2009) Using a semi-quantitative, single-cell sensitive RT-PCR method, we studied the expression of oogenesis specific genes (Nobox, Oct4, Bmp15, Gdf9, Oogenesin1 and Oogenesin2) in single oocytes collected from primordial, primary, secondary, preantral and antral follicles during natural and gonadotropin-induced mouse follicular development. We compared the number of transcripts of these genes, showing that they are differentially expressed, both in natural conditions and under gonadotropin-induction throughout the assessed developmental stages. Our data show a clear increase in the number of transcripts between the primordial until the preantral stages, with the exception of the Oogenesin1 transcripts under gonadotropin-induction. The number of transcripts starts decreasing at the antral stage and proceeds until the metaphase II stage, with values very similar to those obtained for the primordial oocytes in both analyzed conditions. Under exogenous gonadotropin-induction, oocyte recruitment to ovulation at the preantral stage is marked by an increase in Nobox and Oogenesin2 gene expression that is concomitant with a decrease in Oogenesin1 gene expression. Oocytes that are able to proceed into whole embryo development show a tight regulation of Nobox and Oct4 expression at the antral stage. A parallel immunocytochemical study at the protein level corroborates these findings.//////////////////
The promoter of the oocyte-specific gene, oog1, functions in both male and female meiotic germ cells in transgenic mice. Ishida M 2013 et al.
Oog1 is an oocyte-specific gene whose expression is turned on in mouse oocytes at embryonic day (E) 15.5, concomitant with the time when most of the female germ cells stop proliferating and enter meiotic prophase. Here, we characterize the Oog1 promoter, and show that transgenic GFP reporter expression driven by the 2.7 kb and 3.9 kb regions upstream of the Oog1 transcription start site recapitulates the intrinsic Oog1 expression pattern. In addition, the 3.9 kb upstream region exhibits stronger transcriptional activity than does the 2.7 kb region, suggesting that regulatory functions might be conserved in the additional 1.2 kb region found within the 3.9 kb promoter. Interestingly, the longer promoter (3.9 kb) also showed strong activity in male germ cells, from late pachytene spermatocytes to elongated spermatids. This is likely due to the aberrant demethylation of two CpG sites in the proximal promoter region. One was highly methylated in the tissues in which GFP expression was suppressed, and another was completely demethylated only in Oog1pro3.9 male and female germ cells. These results suggest that aberrant demethylation of the proximal promoter region induced ectopic expression in male germ cells under the control of 3.9 kb Oog1 promoter. This is the first report indicating that sex-dependent gene expression is altered according to the length and the methylation status of the promoter region. Additionally, our results show that individual CpG sites are differentially methylated and play different roles in regulating promoter activity and gene transcription.
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Expression regulated by
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Ovarian localization
Oocyte
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Genomewide discovery and classification of candidate ovarian fertility genes in the mouse. Gallardo TD et al. Female infertility syndromes are among the most prevalent chronic health disorders in women, but their genetic basis remains unknown because of uncertainty regarding the number and identity of ovarian factors controlling the assembly, preservation, and maturation of ovarian follicles. To systematically discover ovarian fertility genes en masse, we employed a mouse model (Foxo3) in which follicles are assembled normally but then undergo synchronous activation. We developed a microarray-based approach for the systematic discovery of tissue-specific genes and, by applying it to Foxo3 ovaries and other samples, defined a surprisingly large set of ovarian factors (n = 348, approximately 1% of the mouse genome). This set included the vast majority of known ovarian factors, 44% of which when mutated produce female sterility phenotypes, but most were novel. Comparative profiling of other tissues, including microdissected oocytes and somatic cells, revealed distinct gene classes and provided new insights into oogenesis and ovarian function, demonstrating the utility of our approach for tissue-specific gene discovery. This study will thus facilitate comprehensive analyses of follicle development, ovarian function, and female infertility. This is an oocyte-specific gene.
Follicle stages
Primary, Secondary, Antral, Preovulatory
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Oogenesin is a novel mouse protein expressed in oocytes and early cleavage-stage embryos. Minami N et al. We describe a new gene (Oogenesin) that is expressed through oogenesis and early embryogenesis in the mouse. De novo expression starts at 15.5 dpc (days postcoitum) in the ovary, which coincides with the start of oogenesis. The isolated cDNA was 1387 base pairs (bp) in length with a single open reading frame of 326 amino acids corresponding to a predicted molecular mass of 37 kDa with no significant homology to previously reported sequences. A remarkable characteristic of the gene is the presence of a leucine zipper structure at amino acid positions 131-152 and a leucine-rich domain at positions 131-254. Northern blot analysis demonstrated that the mRNA was present only in the ovary, in which it was expressed as a single transcript of approximately 1.7 kb. In situ hybridization revealed distinct signals in the oocytes in follicles at all stages (primordial to antral follicles). Western blot analysis demonstrated that the protein is expressed from oocytes to four-cell-stage embryos and that it has a little larger size (46 kDa) than the predicted size of 37. Immunohistochemical analysis of ovary sections revealed that the protein is also expressed specifically in oocytes in follicles at all stages. Furthermore, immunostaining of preimplantation embryos revealed that the protein localizes in nuclei at the late one-cell and early two-cell stages. These results suggest that the gene has some roles in zygotic transcription of early preimplantation embryos as well as folliculogenesis and oogenesis in the mouse.