Identification of common polymorphisms in the coding sequence of the human MSH receptor (MCIR) with possible biological effects

✍ Scribed by Sandhya V. Koppula; Linda S. Robbins; Dongsi Lu; Eric Baack; Clifton R. White Jr.; Neil A. Swanson; Roger D. Cone

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 214 KB
• Volume: 9
• Category: Article
• ISSN: 1059-7794
• DOI: 10.1002/(sici)1098-1004(1997)9:1<30::aid-humu5>3.0.co;2-t

✦ Synopsis

The extension locus has been identified in many mammalian species as a gene that determines the relative amounts of eumelanin and phaeomelanin pigments in hair and skin. In at least three species, this locus has been demonstrated to encode the melanocyte-stimulating hormone receptor (MC1-R), and functionally variant alleles have been demonstrated to cause a broad range of pigmentation phenotypes. To test for MC1-R allelic variation in man, genomic DNA was extracted from skin samples collected from patients with different skin types (I-VI), and eye and hair color. A PCR-based approach was used to amplify the full length coding sequence of the MC1-R and the resulting products were sequenced. Two polymorphic alleles were identified with single point mutations in the coding sequence: a valine-to-methionine substitution at position 92 (V92M), and an aspartic acid-to-glutamic acid substitution at position 84 (D84E). RFLP analysis demonstrated the presence of the V92M allele in 4 out of 60 (6.6%) of individuals examined, predominantly those with blue eyes and blond hair. This polymorphism was found in both heterozygous and homozygous states in individuals with type I skin. The D84E allele was found in one individual with skin type I; this person also has the V92 M allele and thus is a compound heterozygote.