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Human pigmentation phenotype: a point mutation generates nonfunctional MSH receptor
P A Frändberg1, M Doufexis, S Kapas
1Division of Biological Research on Drug Dependence, Biomedical Centre, Uppsala, Sweden.
Summary
Researchers discovered a nonfunctional melanocortin 1 receptor (MC1R) variant in a person with red hair. This mutation prevents cyclic AMP production, explaining light skin and poor tanning.
Area of Science:
- Genetics
- Dermatology
- Molecular Biology
Background:
- The melanocortin 1 receptor (MC1R) is crucial for regulating human skin and hair pigmentation.
- alpha-Melanocyte stimulating hormone (alpha-MSH) interacts with MC1R to control pigment production.
Purpose of the Study:
- To identify genetic variants of MC1R associated with pigmentation phenotypes.
- To characterize the functional impact of a novel MC1R variant found in an individual with red hair and light skin.
Main Methods:
- Genomic DNA isolation from a subject with skin type I.
- Binding assays using radio-labelled alpha-MSH analogue.
- Measurement of cyclic AMP (cAMP) production in response to receptor stimulation.
Main Results:
- A novel Arg151Cys variant of the human MC1R was identified.
- The Arg151Cys variant exhibited normal binding affinity for alpha-MSH.
- The variant MC1R failed to stimulate cyclic AMP production, indicating complete loss of function.
Conclusions:
- The Arg151Cys MC1R mutation is nonfunctional, leading to red hair, light skin, and poor tanning.
- This is the first reported instance of a nonfunctional MC1R identified in a human subject.
- The findings provide a molecular explanation for the pigmentation phenotype observed.