Genes and ultrastructure in amelogenesis imperfecta

Objectives: Amelogenesis imperfectas (AI) are a group of disorders with obvious clinical and genetic heterogeneity, causing abnormalities in the amount, structure, and composition of enamel. Mutations on amelogenin, enamelin, kallikrein 4, and enamelysin gene have been found to be responsible for AI with different clinical phenotypes and hereditary modes. The causative genes for AI have not been identified in a Chinese population. The aim of the present study is to investigate Chinese families with diverse forms of AI, the possible mutations on candidate genes and ultrastructure on the affected deciduous tooth. Methods: Four Chinese families with amelogenesis imperfecta were investigated and enrolled into the study. Genomic DNA was extracted from peripheral blood samples of members in the four families. Mutation analysis was performed by amplifying all coding regions and splicing junctions of the selected candidate genes and sequencing the products, examining enamelin gene in family 1 and 2, detecting enamelin and kallikrein 4 gene in family 3, screening amelogenin gene in family 4. Ultrastructure of the affected deciduous tooth from family 2 was examined by SEM. Results: The hereditary modes in AI families were as follows: family 1 and 2, autosomal dominant AI; family 3, autosomal recessive AI; family 4, X-linked AI. No disease-causing mutations were identified in 4 families. On SEM observation, enamel of the affected deciduous tooth from family 2 is markedly reduced in thickness, lacks a prismatic structure in some areas and has an increased interval width between enamel rods. Conclusions: Enamelin and kallikrein 4 genes were not causative for autosomal dominant and recessive AI in investigated Chinese families. Other genes may be responsible for AI in these families. AI affected deciduous teeth generated abnormalities in the amount as well as the structure of enamel.