THE CLONING AND CHROMOSOMAL MAPPING OF 2 NOVEL HUMAN OPIOID-SOMATOSTATIN-LIKE RECEPTOR GENES, GPR7 AND GPR8, EXPRESSED IN DISCRETE AREAS OFTHE BRAIN

Following the cloning of the opioid receptors mu, kappa, and delta, we conducted a search for related receptors. Using oligonucleotides base d on the opioid and also the structurally related somatostatin recepto rs, we amplified genomic DNA using the polymerase chain reaction and i solated fragments of novel Gr protein-coupled receptor genes. Two of t hese gene fragments designated clones 12 and 11 were used to isolate t he full-length genes, The intronless coding sequences of these genes, named GPR7 and GPR8, shared 70% identity with each other, and each sha red significant similarity with the sequences encoding transmembrane r egions of the opioid and somatostatin receptors. GPR7 was mapped to ch romosome 10q11.2-q21.1 and GPR8 to chromosome 20q13.3. Northern blot a nalysis using human mRNA demonstrated expression of GPR7 mainly in cer ebellum and frontal cortex, while GPR8 was located mainly in the front al cortex. In situ hybridization revealed expression of GPR7 in the hu man pituitary, A partial sequence of the mouse orthologue of GPR7 was obtained, and in situ hybridization demonstrated expression in discret e nuclei of brain, namely suprachiasmatic, arcuate, and ventromedial n uclei of hypothalamus. A stable cell line expressing the GPR7 gene was created, but expression levels of the receptor were low. The availabl e pharmacology indicated binding to several opioid drugs such as brema zocine, levorphanol, and beta-FNA, but not to the opioid receptor subt ype-selective mu, delta, or kappa agonists. (C) 1995 Academic Press,In c.