FGFR2 is associated with hair thickness in Asian populations.

Hair morphology is one of the most differentiated traits among human populations. A previous study has shown that a nonsynonymous single nucleotide polymorphism (SNP) in the EDAR gene, EDAR 1540T/C, is strongly associated with hair thickness in Asian populations. However, the contributions of other genes remain to be elucidated. In this study, 12 SNPs on 10 hair formation-related genes with high differentiation between Asian and other populations were examined to further identify genes associated with hair morphology. A multiple regression analysis adjusted for age, sex, population and the effect of EDAR 1540T/C revealed an SNP in intron 9 of FGFR2, rs4752566, to be significantly associated with hair thickness (cross-sectional area; P-value=0.0052, small diameter; P-value=0.029 and large diameter; P-value=0.0015). In the genomic region containing the FGFR2 gene, rs4752566 was not in strong linkage disequilibrium (LD) with the surrounding SNPs, indicating that the significant association of rs4752566 with the hair thickness is not due to LD with polymorphisms of the other genes. The rs4752566-T allele of FGFR2, associated with thicker hair, was also shown to be associated with higher mRNA level of FGFR2 (P-value=0.0270). These results suggest that the FGFR2 polymorphism affects the variation in hair thickness in Asia through alteration in the expression level of FGFR2.