Hair and teeth are appendages of ectodermal origin, and there are common molecular backgrounds involved in their formation. To date, it has been revealed that a nonsynonymous polymorphism in EDAR has effects on the morphological variation in both hair and teeth. Previous association studies have confirmed that single nucleotide polymorphisms (SNPs) in/near THADA, FRAS1, WNT10A, NAF1 and FGFR2 are associated with hair morphology.
In this study, we thus examined whether these SNPs are also associated with dental characteristics. We measured metric dental traits including crown size and also evaluated non-metric dental traits using plaster casts obtained from subjects (272 Japanese and 226 Koreans). DNA samples were prepared from the subjects and genotyped for the hair morphology-associated SNPs. We observed a significant association of crown size with an SNP in WNT10A (rs7349332), but not with SNPs in other genes.
Therefore, we further examined four SNPs within and around WNT10A, among which rs10177996 had the strongest association with dental traits. World distribution of the derived allele in rs10177996, which is associated with larger teeth, showed that Eurasians have a higher allele frequency than Africans. Together with previous studies on hair morphology, this study demonstrated that common variations in WNT10A have pleiotropic effects on the morphology of ectodermal appendages.