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The melanocortin 1 receptor (MC1R), one of five genes in a family highly conserved throughout vertebrate ancestry, profoundly influences pigmentation and is the only gene identified that explains substantial variance in human skin and hair color in the general population. Particular mutations at MC1R are associated with red hair, increased prevalence of skin cancer, and a decreased susceptibility to prostate cancer. Reviewed here are several recent population-genetic studies that have investigated these correlations.
A partial cDNA encoding MC1R and full-length cDNAs for MC3R and MC5R were cloned from the brain of a urodele amphibian, the rough skinned newt Taricha granulosa. The deduced proteins contain 193, 322, and 346 amino acids, respectively, and display features conserved among G protein-coupled receptors. Sequence identity for the full-length receptors is greatest to those from the chicken (MC3R, 75.2%; MC5R, 86.8%), while the MC1R partial sequence has slightly greater identity with reptilian receptors (62.7-67.4%) than with MC1R sequences from other vertebrates (58.5-63.7%). Attempts to extend the 581-bp MC1R partial sequence were unsuccessful, though expression of this receptor was further suggested by isolation of a 315-bp fragment from kidney and spleen matching the larger fragment from brain. This is the first report of cDNA sequences coding for melanocortin receptors from an amphibian.