A nonsense mutation in the enamelin gene causes local hypoplastic autosomal dominant amelogenesis imperfecta (AIH2).
Amelogenesis imperfecta (AI) is an inherited tooth disorder affecting tooth enamel formation only. A gene for autosomal dominant AI, the local hypoplastic form, has been localized to a 4 Mb region on chromosome 4q (AIH2). The enamelin gene (ENAM ), has been mapped to chromosome 4q21, to the same region as AIH2, and was recently shown to be mutated in patients with smooth and thin hypoplastic autosomal dominant AI (ADAI). In this study, we describe an ENAM mutation causing the local hypoplastic form of ADAI, a phenotype that accounts for 27% of the autosomally inherited cases in Northern Sweden. This nonsense mutation in the enamelin gene results in a truncated peptide of 52 amino acids as compared with 1142 amino acids of the normal protein. Our results show that while a splice site mutation is associated with smooth and thin hypoplastic AI, a base substitution resulting in a shorter peptide causes local hypoplasia of the enamel, a milder form of AI. These findings support ENAM as a disease gene, and shed new light on the molecular mechanism of the disease and to the function of the enamelin protein in enamel formation.
Mårdh
Carina K
CK
Department of Medical Genetics/Medical Biosciences, Umeå University, S-901 87 Umeå, Sweden. carina.karman-mardh@astrazeneca.com
Bäckman
Birgitta
B
Holmgren
Gösta
G
Hu
Jan C-C
JC
Simmer
James P
JP
Forsman-Semb
Kristina
K
D000567:Amelogenesis Imperfecta / Q000235:genetics*; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics; D018389:Codon, Nonsense / Q000235:genetics*; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D003746:Dental Enamel Proteins / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D005799:Genes, Dominant; D006801:Humans; D008297:Male; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction
D018389:Codon, Nonsense; D017931:DNA Primers; D003746:Dental Enamel Proteins; C038456:tuftelin