ASSESSMENT OF MC1R AND α-MSH GENE SEQUENCES IN IRANIAN VITILIGO PATIENTS

Molecular Genetics and Epidemiology of Vitiligo: A Minireview

Background and aims: Vitiligo is an acquired, idiopathic, and common depigmentation disorder of the skin that affects people of all ages and both sexes equally worldwide. Although etiology of the disease is unknown, there are theories such as environment and genetic factors. Methods: In this article, we collected and summarized the appropriate manuscripts regarding the epidemiology and genetics using the terms vitiligo and genetic epidemiology in PubMed and Google Scholar. Results: Studies showed the highest prevalence of disease in African countries, but with regard to the distribution of disease in different areas, environmental factors were as important as other causes of vitiligo, and 3 genes of FOXP3, XBP1 and TSLP had the most association with the disease. Conclusion: It seems that recognition of the genetic basis of vitiligo will supply new insight into the therapies for it. Therefore, more genetic studies are needed to discover the genes and causes linked to clinical aspects of this disease.

Modern vitiligo genetics sheds new light on an ancient disease

Vitiligo is a complex disorder in which autoimmune destruction of melanocytes results in white patches of skin and overlying hair. Over the past several years, extensive genetic studies have outlined a biological framework of vitiligo pathobiology that underscores its relationship to other autoimmune diseases. This biological framework offers insight into both vitiligo pathogenesis and perhaps avenues towards more effective approaches to treatment and even disease prevention.

Simultaneous purifying selection on the ancestral MC1R allele and positive selection on the melanoma-risk allele V60L in south Europeans

In humans, the geographical apportionment of the coding diversity of the pigmentary locus melanocortin-1 receptor (MC1R) is, unusually, higher in Eurasians than in Africans. This atypical observation has been interpreted as the result of purifying selection due to functional constraint on MC1R in high UV-B radiation environments. By analyzing 3,142 human MC1R alleles from different regions of Spain in the context of additional haplotypic information from the 1000 Genomes (1000G) Project data, we show that purifying selection is also strong in southern Europe, but not so in northern Europe. Furthermore, we show that purifying and positive selection act simultaneously on MC1R. Thus, at least in Spain, regions at opposite ends of the incident UV-B radiation distribution show significantly different frequencies for the melanoma-risk allele V60L (a mutation also associated to red hair and fair skin and even blonde hair), with higher frequency of V60L at those regions of lower incident UV-B radiation. Besides, using the 1000G south European data, we show that the V60L haplogroup is also characterized by an extended haplotype homozygosity (EHH) pattern indicative of positive selection. We, thus, provide evidence for an adaptive value of human skin depigmentation in Europe and illustrate how an adaptive process can simultaneously help to maintain a disease-risk allele. In addition, our data support the hypothesis proposed by Jablonski and Chaplin (Human skin pigmentation as an adaptation to UVB radiation. Proc Natl Acad Sci U S A. 2010;107:8962-8968), which posits that habitation of middle latitudes involved the evolution of partially depigmented phenotypes that are still capable of suitable tanning.