Isolation and tissue expression of Opn5 (neuropsin) genes from Danio rerio (zebrafish) and Xenopus laevis.

Abstract

Abstract: : Purpose: To isolate and characterise the tissue expression of the zebrafish and Xenopus orthologues of Opn5 (neuropsin), a novel opsin recently identified in mammalian retina and brain (Tarttelin et al., 2003, FEBS Letters 554, 410). Methods: BLAST database analysis using the mouse Opn5 sequence as a search tool identified putative zebrafish Opn5 genomic DNA sequence matches, and a Xenopus EST clone sequence match. The cDNA for the zebrafish Opn5 gene was cloned and sequenced from zebrafish eye mRNA by reverse transcriptase polymerase chain reaction (RT–PCR) amplification using primers designed to these sequence matches. The coding region was completed by 3 RACE PCR. RT–PCR was used to analyse the tissue expression pattern of both the zebrafish and Xenopus Opn5 genes. Results: A zebrafish cDNA comprising the full–length coding region of neuropsin (Opn5) has been cloned and sequenced from zebrafish eye tissue. The deduced amino acid sequence predicts a protein of 352 amino acids, which exhibits 68 % and 70 % amino acid identity to mouse and human OPN5 respectively. The Xenopus EST clone identified during the database searches was obtained, sequenced and found to contain the full length coding sequence of Xenopus Opn5. The predicted Xenopus protein, comprising 341 amino acids exhibits 72 % identity to both human and mouse Opn5, and 71 % identity to the zebrafish protein. Phylogenetic analysis indicates that the zebrafish and Xenopus Opn5 segregate with mammalian Opn5. RT–PCR was used to investigate the tissue expression pattern of neuropsin in both zebrafish and Xenopus. Opn5 is expressed in the eye, brain and the skin in both species. Conclusions: The zebrafish and Xenopus laevis orthologues of the novel opsin gene Opn5 have been cloned and sequenced from adult eye tissue. Like the mammalian Opn5 genes, both orthologues are expressed in the eye and brain.

Keywords: opsins • gene/expression