Common Variants in the Trichohyalin Gene Are Associated with Straight Hair in Europeans

The study identified common variants in the Trichohyalin gene (TCHH) associated with straight hair in Europeans through a genome-wide association scan involving 16,140 individuals of European descent. These variants explained approximately 6% of the variance in hair morphology and were most frequent in Northern Europeans. The findings paralleled the distribution of the straight-hair EDAR variant in Asian populations. The study's robust results were consistent across three Australian samples, accounting for age and phenotypic differences, and showed no evidence of epistasis or sex heterogeneity. The variant rs11803731, which replaces leucine with methionine at position 790 of the TCHH protein, showed the highest frequency in Northern Europeans and suggested a potential regulatory role rather than a structural one.