Molecular cloning of a fish gene encoding a novel seven-transmembrane receptor related distantly to catecholamine, histamine, and serotonin receptors

A genomic DNA fragment encoding a G protein-coupled seven-transmembrane receptor was isolated from Medaka fish, Oryzias latipes. The encoded protein is similar in sequence to other receptors including catecholamine, histamine and serotonin receptors. However, the similarity is much lower than those among members of these receptor subfamilies, thus suggesting this seven-transmembrane receptor to be an orphan receptor whose ligand has not yet been identified. Genomic Southern blot analysis suggested that the fish genome contains additional receptor genes related to the isolated gene, indicating that this novel receptor, possibly with its related receptors, might constitute a novel subfamily of the seven-transmembrane receptor superfamily.