Genetic determinants of hair and eye colours in the Scottish and Danish populations

Abstract

BackgroundEye and hair colour is highly variable in the European population, and is largely genetically determined. Both linkage and association studies have previously been used to identify candidate genes underlying this variation. Many of the genes found were previously known as underlying mutant mouse phenotypes or human genetic disease, but others, previously unsuspected as pigmentation genes, have also been discovered.ResultsWe assayed the hair of a population of individuals of Scottish origin using tristimulus colorimetry, in order to produce a quantitative measure of hair colour. Cluster analysis of this data defined two groups, with overlapping borders, which corresponded to visually assessed dark versus red/light hair colour. The Danish population was assigned into categorical hair colour groups. Both cohorts were also assessed for eye colour. DNA from the Scottish group was genotyped at SNPs in 33 candidate genes, using 384 SNPs identified by HapMap as representatives of each gene. Associations found between SNPs and colorimetric hair data and eye colour categories were replicated in a cohort of the Danish population. The Danish population was also genotyped with SNPs in 4 previously described pigmentation genes. We found replicable associations of hair colour with the KITLG and OCA2 genes. MC1R variation correlated, as expected, with the red dimension of colorimetric hair colour in Scots. The Danish analysis excluded those with red hair, and no associations were found with MC1R in this group, emphasising that MC1R regulates the colour rather than the intensity of pigmentation. A previously unreported association with the HPS3 gene was seen in the Scottish population. However, although this replicated in the smaller cohort of the Danish population, no association was seen when the whole study population was analysed.ConclusionsWe have found novel associations with SNPs in known pigmentation genes and colorimetrically assessed hair colour in a Scottish and a Danish population.

Colorful DNA polymorphisms in humans

“…KITLG mutations have been found to cause familial progressive hyperand hypopigmentation [152,153]. Variants at the KITLG locus have been associated with light hair colors in Europeans [17,147,154]. The associated SNP rs12821256 at KITLG was shown to have a small but independent contribution to categorical hair color prediction in Polish Europeans [94].…”

Distribution of an allele associated with blond hair color across northern island melanesia

“…Studies of hair pigmentation variation and its underlying genetic causes have largely focused on populations of European descent, where hair color can range from very light blond to red, brown, and dark black (Valverde et al, 1995;Smith et al, 1998;Grimes et al, 2001;Sturm et al, 2003;Branicki et al, 2007;Sulem et al, 2007;Vaughn et al, 2008;Han et al, 2008;Kayser and Schneider, 2009;Mengel-From et al, 2009;Branicki et al, 2011;Draus-Barini et al, 2013;Walsh et al, 2013). A limited number of quantitative assessments of hair color in non-European populations indicate that there is substantially less variation in these groups than found in European populations (Shriver and Parra, 2000;Norton et al, 2006).…”

Prediction Model Validation: Normal Human Pigmentation Variation

“…These models are merely a starting place to predict normal human pigmentation variation, independent of ethnic origin. Other studies have developed prediction models for eye, skin, and hair color [38][39][40][41][42][43]. However, with the exception of the study by Spichenok et al, these studies trained their models utilizing a population of exclusively European descent.…”