title: Human enamel thickness and ENAM polymorphism.
abstract: The tooth enamel development gene, enamelin (ENAM), showed evidence of positive selection during a genome-wide scan of human and primate DNA for signs of adaptive evolution. The current study examined the hypothesis that a single-nucleotide polymorphism (SNP) C14625T (rs7671281) in the ENAM gene identified in the genome-wide scan is associated with a change in enamel phenotype. African Americans were selected as the target population, as they have been reported to have a target SNP frequency of approximately 50%, whereas non-Africans are predicted to have a 96% SNP frequency. Digital radiographs and DNA samples from 244 teeth in 133 subjects were analysed, and enamel thickness was assessed in relation to SNP status, controlling for age, sex, tooth number and crown length. Crown length was found to increase with molar number, and females were found to have thicker enamel. Teeth with larger crowns also had thicker enamel, and older subjects had thinner enamel. Linear regression and generalized estimating equations were used to investigate the relationship between enamel thickness of the mandibular molars and ENAM SNP status; enamel in subjects with the derived allele was significantly thinner (P=0.040) when the results were controlled for sex, age, tooth number and crown length. The derived allele demonstrated a recessive effect on the phenotype. The data indicate that thinner dental enamel is associated with the derived ENAM genotype. This is the first direct evidence of a dental gene implicated in human adaptive evolution as having a phenotypic effect on an oral structure.
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Diane M
authors.initials: DM
authors.lastname: Daubert
authors.affiliation: Center for Reproductive Biology and School of Biological Sciences, Washington State University, Pullman, USA.
authors.forename: Joanna L
authors.initials: JL
authors.lastname: Kelley
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Yuriy G
authors.initials: YG
authors.lastname: Udod
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Carolina
authors.initials: C
authors.lastname: Habor
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Chris G
authors.initials: CG
authors.lastname: Kleist
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Ilona K
authors.initials: IK
authors.lastname: Furman
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.|Department of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas, USA.
authors.forename: Igor N
authors.initials: IN
authors.lastname: Tikonov
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, USA.
authors.forename: Willie J
authors.initials: WJ
authors.lastname: Swanson
authors.affiliation: Department of Periodontics, University of Washington, Seattle, USA.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Roberts
mesh_terms: D000566:Amelogenesis; D000818:Animals; D003743:Dental Enamel; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008963:Molar; D011323:Primates; D014070:Tooth
chemical_list: C550525:ENAM protein, human; D016326:Extracellular Matrix Proteins