Submitted to: Molecular Reproduction and Development
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/13/2007
Publication Date: 5/1/2008
Citation: Qiu, G., Weber, G.M., Rexroad III, C.E., Yao, J. 2008. Identification of RtGST-1, a novel germ cell-specific mRNA-like transcript predominantly expressed in early previtellgenic oocytes in rainbow trout (Oncorhynchus mykiss). Molecular Reproduction and Development. 75:723-30. Interpretive Summary: Although an estimated 98% of the genome can be transcribed into RNA, only about 1.2% actually encodes proteins. In recent years, several thousand non-protein coding RNAs (ncRNAs) have been identified in various organisms. Many have been unexpectedly identified through extensive RNA sequencing projects in mammals. In an effort to characterize the oocyte transcriptome and identify novel oocyte-expressed genes potentially involved in oocyte/follicular development and early embryogenesis in rainbow trout, we have recently constructed a rainbow trout oocyte cDNA library and generated ~ 20,000 RNA sequences . A significant number of novel transcripts have been identified including one that is oocyte-specific and encodes a protein with a conserved hormone binding protein site. Here, we report the identification of a novel non-protein coding mRNA-like germ cell-specific transcript (named RtGST-1), and its differential expression profiles during gametogenesis and early embryogenesis which suggest a unique role in each process.
Technical Abstract: Noncoding mRNA-like transcripts play important roles in a wide range of biological events such as cell differentiation and organogenesis. We report here the identification of a novel germ cell-specific mRNA-like transcript (RtGST-1) from a rainbow trout oocyte cDNA library. The novel transcript of 1165 bp was confirmed to be full-length based on Northern blot and 5’RACE analyses. The transcript is polyadenylated but does not contain a significant open reading frame (ORF). The presumable ORF (encodes a peptide of 71 amino acids) has poor codon usage for rainbow trout and the AUG codon is in a poor context for translation initiation. RT-PCR showed that the novel gene is specifically expressed in various stage ovaries and immature testes. In situ hybridization analysis demonstrated that the novel transcript is localized exclusively in early previtellogenic oocytes and spermatocytes. The study represents the first report of a germline-specific mRNA-like transcript in fish.