Variation in the RPTN gene may facilitate straight hair formation in Europeans and East Asians

Head hair shape is a distinctive feature of human appearance and shows a marked degree of variation on the world map. TCHH and EDAR, the two major hair shape genes, have been shown to influence hair structure exclusively in Europe and East Asia, respectively, indicating divergent genetic mechanisms of straight hair formation in various human populations [1–3]. However, the proportion of known heritability explained by both genes in respective populations is very small. Although genome-wide association studies have been shown to be effective in identifying genes with medium to small effect sizes, there are clear evidences that essential fraction of the overall heritability for complex traits is not properly identified using standard approaches.