ENAM Mutations in Autosomal-dominant Amelogenesis Imperfecta
J.-W. Kim1,2,
F. Seymen3,
B.P.-J. Lin4,
B. Kiziltan3,
K. Gencay3,
J.P. Simmer1, and
J.C.-C. Hu1,*
1 Department of Orthodontics and Pediatric Dentistry, University of Michigan Dental Research Lab, 1210 Eisenhower Place, Ann Arbor, MI 48108, USA;
2 Seoul National University, College of Dentistry, Department of Pediatric Dentistry & Dental Research Institute, 28-2 Yongon-dong, Chongno-gu, Seoul, Korea 110-768;
3 University of Istanbul, Faculty of Dentistry, Department of Pedodontics, Çapa, Istanbul, Turkey; and
4 UCSF School of Dentistry, Department of Growth and Development, San Francisco, CA 94143-0640, USA;
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Figure 1. Enamelin gene structure and mutations that cause autosomal-dominant amelogenesis imperfecta. The structure of the human enamelin gene showing the positions of 5 known mutations in an AI kindred is shown at the top. The exons are blocks numbered 1 through 10; the introns are lines. Below each exon is the range of amino acids in the enamelin protein encoded by the exon. The lower box shows the predicted effect of each mutation on the protein, the location of the mutation in the cDNA and gene, the type of enamel defect, and the reference(s) where each mutation is described.
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Figure 2. Oligonucleotide primers used to amplify ENAM coding exons and determine their DNA sequence. On the upper right is a 1% agarose gel, stained with ethidium bromide, showing each PCR amplification product that was used to identify the enamelin gene mutations. Above each band is the number of the ENAM exon that was amplified; below each band is the predicted length of the PCR amplification product. The exon-specific PCR amplification primer pairs (F = forward; R = reverse) and their annealing temperatures (T°C) are listed. The reactions had a five-minute denaturation at 94°C, followed by 40–50 cycles each with denaturation at 94°C for 30 sec, primer annealing at 55–61°C for 30 sec, and product extension at 72°C for 30–60 sec. In the final cycle, the 72°C extension was for 7 min.
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Figure 3. Family 1. Panel A shows the pedigree, and panel B shows DNA sequencing chromatograms of the exon 8/intron 8 splice junction. The site of the frameshift mutation and the corresponding wild-type (wt) sequences are indicated by arrows (g.8344delG). Panels C and D show a frontal photograph and a panorex radiograph for the proband taken at ages 11 and 6, respectively. Panels E through H show intra-oral photographs and a panorex radiograph taken at age 19. The upper anterior teeth were treated endodontically and restored with composite resin restorations.
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Figure 4. Family 2. Panel A shows the pedigree, and panel B shows DNA sequencing chromatograms of the intron 6/exon 7 splice junction. Arrows indicate the position of the A to C transversion and the corresponding wild-type (wt) sequence (IVS6-2A>C). Panels C through F show intra-oral photographs and a panorex of the proband at age 12.5. Panels G through I show intra-oral photographs and a panorex of the the proband’s 11-year-old brother. Panel J shows an oral photograph of the remaining mandibular anterior teeth of the proband’s mother, taken at age 32.
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