The ovine melatonin-related receptor: Cloning and Preliminary Distribution and Binding Studies

A melatonin-related receptor was cloned from an ovine genomic library, The sequenced gene has a similar structure to that of the melatonin receptor gene family and consists of two exons separated by an intron of approximately 3 kb, Exon 1 and exon 2 of the ovine melatonin-related receptor encode a protein of 575 amino acids which is 73.8% homologous to the human melatonin-related receptor and shows 40.9% homology with the ovine Mel(1a) melatonin receptor. COS-7 cells transiently expressing ovine melatonin-related receptors did not bind 2-[I-125]iodomelatonin or H-3-melatonin. Reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization studies revealed expression of the ovine melatonin-related receptor in the hypothalamus, pituitary, retina and retinal pigment epithelium, Furthermore, expression of the ovine melatonin-related receptor is shown to be coincident with Mel(1a) and 2-[I-125]iodomelatonin binding in the pituitary and serotonin N-acetyl transferase (arylalkylamine N-acetyl transferase, AANAT) expression in the retina. Expression patterns and similarity with the melatonin receptor gene family suggest a role for this novel G protein-coupled receptor in control and regulation of endocrine function and retinal physiology.