New vitiligo susceptibility regions linked to hair, skin, and eye color
MedWire News: Results from a genome-wide association study (GWAS) have identified 13 new regions or loci in the genome linked with vitiligo susceptibility.
The researchers explain that these loci are known to be involved in immune regulation, susceptibility to melanoma, and regulation of hair, skin, and eye color.
Richard Spritz (University of Colorado School of Medicine, Aurora, USA) and colleagues found that people with blue or grey eyes were much less likely to have vitiligo than those with tan or brown eyes.
Conversely, the same people who have a reduced risk for vitiligo are likely to have increased risk for melanoma, say the investigators.
"Genetically, in some ways vitiligo and melanoma are polar opposites. Some of the same genetic variations that make one more likely to have vitiligo make one less likely to have melanoma, and vice-versa," commented Spritz in a press statement.
"Vitiligo is an autoimmune disease, in which a person's immune system attacks their normal pigment cells. We think that vitiligo represents over-activity of a normal process by which one's immune system searches out and destroys early cancerous melanoma cells."
The current study adds to previous research that identified 14 susceptibility loci for vitiligo. Spritz and co-researchers analyzed data from a GWAS (450 vitiligo cases; 3182 controls), a replication cohort (1440 vitiligo cases; 1316 controls), and a meta-analysis (3187 vitiligo cases; 6723 controls) to search for new regions of susceptibility.
In total, 13 new loci were identified, including OCA2-HERC2, MC1R, a region near TYR, IFIH1, CD80, CLNK, BACH2, SLA, CASP7, CD44, IKZF4, SH2B3, and TOB2.
The TYR gene encodes tyrosinase, which is involved in synthesizing melanin. The researchers believe that variation in this gene and in MC1R is linked to vitiligo and malignant melanoma susceptibility, suggesting that "vitiligo may be related to the immune surveillance of melanoma."
The IFIH1, CD80, CASP7, CD44, and BACH2 genes are all thought to be involved in immune regulation, which might be expected as vitiligo is an autoimmune disease, say Spritz et al.
The OCA2 gene is involved in determining eye, hair, and skin color. The team found that alleles of two single nucleotide polymorphisms found in the OCA2-HERC2 area (rs1129038 and rs12913832) that conveyed low risk for vitiligo were strongly linked to grey/blue eye color and a high risk for melanoma.
Confirming their suggestion that vitiligo is associated with having brown/tan eyes, Spritz and team found that in 1206 vitiligo patients of European ancestry, 43.2% had brown/tan eyes and 26.8% had blue/grey eyes compared with a respective 26.5% and 48.9% of people of European ancestry in the USA and Australia without vitiligo.
Writing in Nature Genetics, the researchers conclude that although there may be as yet undiscovered susceptibility loci for vitiligo, the regions and candidate genes identified to date "provide insights into vitiligo pathobiology, the optimal use of existing therapies and even new approaches to treatment."
By Helen Albert