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MMP20 Active-site Mutation in Hypomaturation Amelogenesis Imperfecta

¹ NIDCR, NIH, 10 Center Drive, Building 10, Room 5-2531, Bethesda, MD 20892-1432, USA;
² Istanbul University, School of Dentistry, Istanbul, Turkey;
³ NHGRI, NIH, Bethesda, MD 20892, USA;
⁴ University of Pittsburgh, School of Dental Medicine, Pittsburgh, PA 15261, USA; and
⁵ current address, Department of Pedodontics, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey;

View larger version (29K): [in a new window]   Figure 1. Pedigree, mutation, and biochemical analyses of family segregating autosomal-recessive hypomaturation AI. (A) Pedigree of family. Individuals from whom a blood sample was obtained are shown by an asterisk. Individuals clinically affected with hypomaturation AI are indicated by fully blackened symbols. These individuals are homozygous for the MMP20 g.16250T>A mutation. Carriers of the MMP20 g.16250T>A mutation are shown by partially blackened symbols. The enamel phenotype of all carriers is normal. (B) Mutational analysis of MMP20. The left panel shows the wild-type sequence for part of MMP20 exon 5 (from II-3). The middle panel shows the sequence from the same region of exon 5 from a carrier (III-1), showing the heterozygous missense mutation (g.16250T>A), which results in a p.His226Gln substitution. The right panel shows the sequence from the proband (IV-1), showing the homozygous change. (C) Enzymography of recombinant human wild-type and mutant MMP20. Recombinant human wild-type and mutant MMP20 cDNA were transiently transfected into the human kidney 293 cell line. The culture-conditioned media were collected, concentrated, and run on 4–16% SDS-polyacrylamide gradient gels containing casein. Following electrophoresis and washing, the gel was incubated at 37°C for 2 days in 50 mM Tris buffer (pH 7.4) containing 5 mM CaCl2 and 1 mM MgCl2. Lanes marked by WT indicate recombinant human wild-type MMP20, lanes marked by MT indicate recombinant human mutant MMP20, and EV indicates expression vector only.

View larger version (93K): [in a new window]   Figure 2. Clinical photographs and radiograph of proband (IV-1 in Fig. 1). (A) Frontal view. Proband is in mixed dentition, showing anterior open bite and hypomaturation phenotype. (B) Maxillary occlusal view. Caries is evident on the central incisors and posterior teeth. (C) Mandibular occlusal view. Note extensive attrition of posterior teeth, and caries is evident on the molars. (D) Panoramic radiograph showing mixed dentition and reduced mineralization of the enamel.

View larger version (89K): [in a new window]   Figure 3. Clinical photographs and radiograph of the affected sibling (IV-2 in Fig. 1). (A) Frontal view. Proband is in mixed dentition, showing anterior open bite and hypomaturation phenotype. (B) Maxillary occlusal view. Caries is evident on posterior teeth. (C) Mandibular occlusal view. Caries is evident on posterior teeth. (D) Panoramic radiograph showing mixed dentition and reduced mineralization of the enamel.