Article

The Genetics of Sun Sensitivity in Humans

Systems Group, Dermatology, University of Edinburgh, Edinburgh, United Kingdom.
The American Journal of Human Genetics (Impact Factor: 10.99). 11/2004; 75(5):739-51. DOI: 10.1086/425285
Source: PubMed

ABSTRACT Humans vary >100-fold in their sensitivity to the harmful effects of ultraviolet radiation. The main determinants of sensitivity are melanin pigmentation and less-well-characterized differences in skin inflammation and repair processes. Pigmentation has a high heritability, but susceptibility to cancers of the skin, a key marker of sun sensitivity, is less heritable. Despite a large number of murine coat-color mutations, only one gene in humans, the melanocortin 1 receptor (MC1R), is known to account for substantial variation in skin and hair color and in skin cancer incidence. MC1R encodes a 317-amino acid G-coupled receptor that controls the relative amounts of the two major melanin classes, eumelanin and pheomelanin. Most persons with red hair are homozygous for alleles of the MC1R gene that show varying degrees of diminished function. More than 65 human MC1R alleles with nonsynonymous changes have been identified, and current evidence suggests that many of them vary in their physiological activity, such that a graded series of responses can be achieved on the basis of (i) dosage effects (of one or two alleles) and (ii) individual differences in the pharmacological profile in response to ligand. Thus, a single locus, identified within a Mendelian framework, can contribute significantly to human pigmentary variation.

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    • "It has been suggested that the remaining genetic risks may be due to low-penetrance susceptibility genes, such as the melanocortin-1 receptor (MC1R) gene. MC1R plays a role in pigmentation in several species; also, genetic variants are associated with pigmentary phenotypes in humans, including red hair, pale skin, freckling, and sun sensitivity [4,5]. Indeed, MC1R variants are associated with melanoma susceptibility in several study populations [6-19]. "
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    ABSTRACT: Background Few high penetrance genes are known in Malignant Melanoma (MM), however, the involvement of low-penetrance genes such as MC1R, OCA2, ASIP, SLC45A2 and TYR has been observed. Lately, genome-wide association studies (GWAS) have been the ideal strategy to identify new common, low-penetrance susceptibility loci. In this case–control study, we try to validate in our population nine melanoma associated markers selected from published GWAS in melanoma predisposition. Methods We genotyped the 9 markers corresponding to 8 genes (PARP1, MX2, ATM, CCND1, NADSYN1, CASP8, IRF4 and CYP2R1) in 566 cases and 347 controls from a Spanish population using KASPar probes. Genotypes were analyzed by logistic regression and adjusted by phenotypic characteristics. Results We confirm the protective role in MM of the rs3219090 located on the PARP1 gene (p-value 0.027). Additionally, this SNP was also associated with eye color (p-value 0.002). A second polymorphism, rs12203592, located on the IRF4 gene was associated with protection to develop MM for the dominant model (p-value 0.037). We have also observed an association of this SNP with both lentigines (p-value 0.014) and light eye color (p-value 3.76 × 10-4). Furthermore, we detected a novel association with rs1485993, located on the CCND1 gene, and dark eye color (p-value 4.96 × 10-4). Finally, rs1801516, located on the ATM gene, showed a trend towards a protective role in MM similar to the one firstly described in a GWAS study. Conclusions To our knowledge, this is the first time that these SNPs have been associated with MM in a Spanish population. We confirmed the proposed role of rs3219090, located on the PARP1 gene, and rs12203592, located on the IRF4 gene, as protective to MM along the same lines as have previous genome-wide associated works. Finally, we have seen associations between IRF4, PARP1, and CCND1 and phenotypic characteristics, confirming previous results for the IRF4 gene and presenting novel data for the last two, suggesting that pigmentation characteristics correlated with eye color are potential mediators between PARP1 and MM protection.
    BMC Cancer 03/2013; 13(1):160. DOI:10.1186/1471-2407-13-160 · 3.32 Impact Factor
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    • "Skin pigmentation is strikingly diverse in humans, varying from very dark to very light with increasing distance from the equator (Jablonski and Chaplin 2000). This is likely a result of intense positive selection achieving a balance between UV protection (Armstrong et al. 1997; Palmer et al. 2000; Rees 2004) on one hand and vitamin D synthesis (Branda and Eaton 1978) on the other. Furthermore, it has been suggested that sexual selection via mate choice preference played a role in the diversity of human skin coloration around the world (Aoki 2002). "
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    ABSTRACT: Natural variation in human skin pigmentation is primarily due to genetic causes rooted in recent evolutionary history. Genetic variants associated with human skin pigmentation confer risk of skin cancer and may provide useful information in forensic investigations. Almost all previous gene-mapping studies of human skin pigmentation were based on categorical skin color information known to oversimplify the continuous nature of human skin coloration. We digitally quantified skin color into hue and saturation dimensions for 5,860 Dutch Europeans based on high-resolution skin photographs. We then tested an extensive list of 14,185 single nucleotide polymorphisms in 281 candidate genes potentially involved in human skin pigmentation for association with quantitative skin color phenotypes. Confirmatory association was revealed for several known skin color genes including HERC2, MC1R, IRF4, TYR, OCA2, and ASIP. We identified two new skin color genes: genetic variants in UGT1A were significantly associated with hue and variants in BNC2 were significantly associated with saturation. Overall, digital quantification of human skin color allowed detecting new skin color genes. The variants identified in this study may also contribute to the risk of skin cancer. Our findings are also important for predicting skin color in forensic investigations.
    Human Genetics 10/2012; 132(2). DOI:10.1007/s00439-012-1232-9 · 4.52 Impact Factor
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    • "The human MC1R gene is highly polymorphic (Garcia-Borron et al., 2005) and several variants, such as the Arg 151 Cys (R 151 C) mutation, result in loss of function of MC1R (Ringholm et al., 2004) and are associated with the red hair color phenotype (RHC) (Valverde et al., 1995; Box et al., 1997; Healy et al., 2000; Rees, 2004), poor tanning ability, and elevated risk of melanoma and carcinoma (Palmer et al., 2000; Kennedy et al., 2001; Sturm et al., 2003; Soufir et al., 2009). These variants can bind to a-MSH but are unable to activate adenylate cyclase in cultured cells (Healy et al., 2001; Ringholm et al., 2004; Newton et al., 2005, 2007; Sanchez-Laorden et al., 2007; Herraiz et al., 2009). "
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    ABSTRACT: Ultraviolet A (UVA) radiations are responsible for deleterious effects, mainly due to reactive oxygen species (ROS) production. Alpha-melanocyte stimulating hormone (α-MSH) binds to melanocortin-1 receptor (MC1R) in melanocytes to stimulate pigmentation and modulate cutaneous inflammatory responses. MC1R may be induced in keratinocytes after UV exposure. To investigate the effect of MC1R signaling on UVA-induced ROS (UVA-ROS) production, we generated HaCaT cells that stably express human MC1R (HaCaT-MC1R) or the Arg151Cys (R(151)C) non-functional variant (HaCaT-R(151)C). We then assessed ROS production immediately after UVA exposure and found that: (1) UVA-ROS production was strongly reduced in HaCaT-MC1R but not in HaCaT-R(151)C cells compared to parental HaCaT cells; (2) this inhibitory effect was further amplified by incubation of HaCaT-MC1R cells with α-MSH before UVA exposure; (3) protein kinase A (PKA)-dependent NoxA1 phosphorylation was increased in HaCaT-MC1R compared to HaCaT and HaCaT-R(151)C cells. Inhibition of PKA in HaCaT-MC1R cells resulted in a marked increase of ROS production after UVA irradiation; (4) the ability of HaCaT-MC1R cells to produce UVA-ROS was restored by inhibiting epidermal growth factor receptor (EGFR) or extracellular signal-regulated kinases (ERK) activity before UVA exposure. Our findings suggest that constitutive activity of MC1R in keratinocytes may reduce UVA-induced oxidative stress via EGFR and cAMP-dependent mechanisms.
    Journal of Cellular Physiology 06/2012; 227(6):2578-85. DOI:10.1002/jcp.22996 · 3.87 Impact Factor
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