Functional analysis of human MC1R polymorphisms in directing melanocyte phenotype

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Sunsmart campaigns are a unifying element in the lives of many Australians who wish to ensure protection against the damaging effects of ultraviolet rays in sunlight. Indeed, Australians have the highest incidence of UV-induced melanoma in the world. Although it is evident that lighter skin colours are more susceptible to sun damage, the relationship between sun exposure, skin type and melanoma formation is less clear. An essential first step in understanding the complex interactions that give rise to melanoma, and in identifying individuals that have a high susceptibility, is to reduce phenotypic analyses to genotypic classifications. As pigmentation phenotype is a factor of central importance in determining an individuals risk for melanoma, characterisation of the genes underlying the physical qualities of human eye, hair and skin colour will give a more direct and accurate genotypic assessment of risk. Results from an epidemiology study of melanoma patients in Queensland have identified a number of genetic changes within the melanocyte stimulating hormone receptor (MC1R) gene that associate with skin, hair and eye colour as well as with incidence of melanoma. Further investigation of MC1R gene alleles which segregate with skin and hair colours will provide the beginning for a whole new genotype-based classification of skin colour and melanoma risk, and will significantly contribute to our understanding of what makes some individuals highly susceptible to melanoma while others are not. Indeed, MC1R polymorphisms may numerically be the most important melanoma predisposition gene yet identified, exerting its effects as one of those common genes of small effect which may account for much more of the case load in melanoma than rarer genes of large effect. Studies such as this will enable powerful genotyping methods to be employed in identification of those individuals at highest risk for melanoma and other skin cancers.