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Identification of OORP‐T, a novel oocyte‐specific gene encoding a protein with a conserved oxysterol binding protein domain in rainbow trout
Author(s) -
Ramachandra Raghuveer K.,
Lankford Scott E.,
Weber Gregory M.,
Rexroad Caird E.,
Yao Jianbo
Publication year - 2007
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20628
Subject(s) - biology , complementary dna , open reading frame , gene , microbiology and biotechnology , cdna library , suppression subtractive hybridization , vitellogenesis , expressed sequence tag , trout , genetics , oocyte , peptide sequence , embryo , fishery , fish <actinopterygii>
Genes specifically expressed in oocytes are important for the development of oocytes and early embryos. By analyzing expressed sequence tags (ESTs) from a rainbow trout oocyte cDNA library, we identified a novel EST sequence that does not show homology to any sequences in the GenBank. Analysis of tissue distribution by RT‐PCR revealed that this gene was only expressed in unfertilized oocytes. Sequencing of the EST clone identified a cDNA of 3,163 bp. Northern blot analysis showed the novel gene has a single transcript of 3.4 kb. Additional 5′ sequence was obtained by 5′ RACE, extending the novel cDNA to 3,333 bp. Analysis of the full‐length cDNA identified an open reading frame (ORF) encoding a protein of 564 amino acids. The novel protein contains a conserved oxysterol binding protein (OSBP) domain at the C terminus that is characteristic of OSBP‐related proteins (ORPs) implicated in lipid metabolism. Therefore, we named the novel gene as Oocyte‐specific Oxysterol binding protein Related‐Protein of Trout (OORP‐T). In situ hybridization showed that the OORP‐T mRNA appears to be confined to the cytoplasm of vitellogenic oocytes. Transcription of OORP‐T appears to start during pre‐vitellogenesis and increases steadily, reaching its peak in the late vitellogenic stage. OORP‐T transcript is abundantly present in unfertilized eggs but the level drops significantly in day 2 embryos and continues to decline in day 7 embryos after which it remains low. We propose that OORP‐T may play an important role in the utilization of yolk‐derived lipid products during oocyte development and early stages of embryonic development in rainbow trout. Mol. Reprod. Dev. 74: 502–511, 2007. © 2006 Wiley‐Liss, Inc.