title: A common variation in EDAR is a genetic determinant of shovel-shaped incisors.
abstract: Shovel shape of upper incisors is a common characteristic in Asian and Native American populations but is rare or absent in African and European populations. Like other common dental traits, genetic polymorphisms involved in the tooth shoveling have not yet been clarified. In ectodysplasin A receptor (EDAR), where dysfunctional mutations cause hypohidrotic ectodermal dysplasia, there is a nonsynonymous-derived variant, 1540C (rs3827760), that has a geographic distribution similar to that of the tooth shoveling. This allele has been recently reported to be associated with Asian-specific hair thickness. We aimed to clarify whether EDAR 1540C is also associated with dental morphology. For this purpose, we measured crown diameters and tooth-shoveling grades and analyzed the correlations between the dental traits and EDAR genotypes in two Japanese populations, inhabitants around Tokyo and in Sakishima Islands. The number of EDAR 1540C alleles in an individual was strongly correlated with the tooth-shoveling grade (p = 7.7 x 10(-10)). The effect of the allele was additive and explained 18.9% of the total variance in the shoveling grade, which corresponds to about one-fourth of the heritability of the trait reported previously. For data reduction of individual-level metric data, we applied a principal-component analysis, which yielded PC1-4, corresponding to four patterns of tooth size; this result implies that multiple factors are involved in dental morphology. The 1540C allele also significantly affected PC1 (p = 4.9 x 10(-3)), which denotes overall tooth size, and PC2 (p = 2.6 x 10(-3)), which denotes the ratio of mesiodistal diameter to buccolingual diameter.
authors.affiliation: Transdisciplinary Research Organization for Subtropics and Island Studies, University of the Ryukyus, Okinawa, 903-0215, Japan. rkimura@lab.u-ryukyu.ac.jp
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kimura
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Mayako
authors.initials: M
authors.lastname: Takeda
authors.forename: Osamu
authors.initials: O
authors.lastname: Kondo
authors.forename: Takashi
authors.initials: T
authors.lastname: Toma
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Haneji
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Hanihara
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Matsukusa
authors.forename: Shoji
authors.initials: S
authors.lastname: Kawamura
authors.forename: Koutaro
authors.initials: K
authors.lastname: Maki
authors.forename: Motoki
authors.initials: M
authors.lastname: Osawa
authors.forename: Hajime
authors.initials: H
authors.lastname: Ishida
authors.forename: Hiroki
authors.initials: H
authors.lastname: Oota
mesh_terms: D000483:Alleles; D053339:Edar Receptor / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D016678:Genome; D005838:Genotype; D006801:Humans; D007564:Japan; D008297:Male; D008957:Models, Genetic; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D025341:Principal Component Analysis; D012044:Regression Analysis; D014070:Tooth / Q000033:anatomy & histology* / Q000502:physiology
chemical_list: C506008:EDAR protein, human; D053339:Edar Receptor