Related Experiment Videos
Identification of common polymorphisms in the coding sequence of the human MSH receptor (MCIR) with possible
S V Koppula1, L S Robbins, D Lu
1Vollum Institute for Advanced Biomedical Research, Portland, Oregon 97201, USA.
Abstract:
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.
Insights
Researchers identified two genetic variations in the melanocyte-stimulating hormone receptor (MC1-R) gene. These MC1-R gene variants are linked to differences in human hair and skin pigmentation, particularly in individuals with lighter complexions.
Area of Science:
- Genetics
- Molecular Biology
- Dermatology
Background:
- The extension locus regulates eumelanin and phaeomelanin production in mammals.
- The melanocyte-stimulating hormone receptor (MC1-R) gene is often responsible for the extension locus.
- MC1-R variants influence pigmentation phenotypes across various species.
Purpose of the Study:
- To investigate allelic variations of the MC1-R gene in humans.
- To correlate MC1-R polymorphisms with human skin, hair, and eye color.
Main Methods:
- Genomic DNA extraction from human skin samples.
- Polymerase Chain Reaction (PCR) amplification of the full MC1-R coding sequence.
- DNA sequencing and Restriction Fragment Length Polymorphism (RFLP) analysis.
Main Results:
- Identified two single point mutations in the MC1-R coding sequence: V92M and D84E.
- The V92M allele was found in 6.6% of individuals, primarily those with blond hair and blue eyes.
- The D84E allele was identified in one individual with type I skin, who was also a compound heterozygote for V92M.
Conclusions:
- Allelic variation in the human MC1-R gene contributes to pigmentation diversity.
- Specific MC1-R polymorphisms are associated with lighter hair, eye, and skin color phenotypes.
- Further research into MC1-R function can elucidate human pigmentation genetics.