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Dean MC, Rosas A, Estalrrich A, García-Tabernero A, Huguet R, Lalueza-Fox C, Bastir M, de la Rasilla M. Longstanding dental pathology in Neandertals from El Sidrón (Asturias, Spain) with a probable familial basis. J Hum Evol 2013; 64:678-86. [PMID: 23615378 DOI: 10.1016/j.jhevol.2013.03.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 10/26/2022]
Abstract
Two Neandertal specimens from El Sidrón, northern Spain, show evidence of retained left mandibular deciduous canines. These individuals share the same mitochondrial (mtDNA) haplotype, indicating they are maternally related and suggesting a potential heritable basis for these dental anomalies. Radiographs and medical CT scans provide evidence of further, more extensive dental pathology in one of these specimens. An anomalous deciduous canine crown morphology that developed before birth subsequently suffered a fracture of the crown exposing the pulp sometime after eruption into functional occlusion. This led to death of the tooth, periapical granuloma formation and arrested deciduous canine root growth at an estimated age of 2.5 years. At some point the underlying permanent canine tooth became horizontally displaced and came to lie low in the trabecular bone of the mandibular corpus. A dentigerous cyst then developed around the crown. Anterior growth displacement of the mandible continued around the stationary permanent canine, leaving it posteriorly positioned in the mandibular corpus by the end of the growth period beneath the third permanent molar roots, which, in turn, suggests a largely horizontal growth vector. Subsequent longstanding repeated infections of the expanding cyst cavity are evidenced by bouts of bone deposition and resorption of the boundary walls of the cyst cavity. This resulted in the establishment of two permanent bony drainage sinuses, one through the buccal plate of the alveolar bone anteriorly, immediately beneath the infected deciduous canine root, and the other through the buccal plate anterior to the mesial root of the first permanent molar. It is probable that this complicated temporal sequence of dental pathologies had an initial heritable trigger that progressed in an unusually complex way in one of these individuals. During life, this individual may have been largely unaware of this ongoing pathology.
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Affiliation(s)
- M C Dean
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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2
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Yaprak E, Subaşı MG, Avunduk M, Aykent F. Amelogenesis imperfecta and generalized gingival overgrowth resembling hereditary gingival fibromatosis in siblings: a case report. Case Rep Dent 2012; 2012:428423. [PMID: 23091740 PMCID: PMC3474234 DOI: 10.1155/2012/428423] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 09/12/2012] [Indexed: 11/17/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a group of hereditary disorders primarily characterized by developmental abnormalities in the quantity and/or quality of enamel. There are some reports suggesting an association between AI and generalized gingival enlargement. This paper describes the clinical findings and oral management of two siblings presenting both AI and hereditary gingival fibromatosis (HGF) like generalized gingival enlargements. The treatment of gingival enlargements by periodontal flap surgery was successful in the management of the physiologic gingival form for both patients in the 3-year follow-up period. Prosthetic treatment was also satisfactory for the older patient both aesthetically and functionally.
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Affiliation(s)
- Emre Yaprak
- Department of Periodontology, Faculty of Dentistry, Kocaeli University, Kocaeli, Turkey
| | - Meryem Gülce Subaşı
- Department of Prosthodontics, Faculty of Dentistry, Aydın University, İzzettin Çalışlar Cad., No. 31/A, Bahçelievler, İstanbul, Turkey
| | - Mustafa Avunduk
- Department of Pathology, Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey
| | - Filiz Aykent
- Department of Prosthodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey
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3
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Abstract
Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principels of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties and the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth.
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Affiliation(s)
- Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA.
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Lopez-Valenzuela M, Ramírez O, Rosas A, García-Vargas S, de la Rasilla M, Lalueza-Fox C, Espinosa-Parrilla Y. An ancestral miR-1304 allele present in Neanderthals regulates genes involved in enamel formation and could explain dental differences with modern humans. Mol Biol Evol 2012; 29:1797-806. [PMID: 22319171 DOI: 10.1093/molbev/mss023] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Genetic changes in regulatory elements are likely to result in phenotypic effects that might explain population-specific as well as species-specific traits. MicroRNAs (miRNAs) are posttranscriptional repressors involved in the control of almost every biological process. These small noncoding RNAs are present in various phylogenetic groups, and a large number of them remain highly conserved at the sequence level. MicroRNA-mediated regulation depends on perfect matching between the seven nucleotides of its seed region and the target sequence usually located at the 3' untranslated region of the regulated gene. Hence, even single changes in seed regions are predicted to be deleterious as they may affect miRNA target specificity. In accordance to this, purifying selection has strongly acted on these regions. Comparison between the genomes of present-day humans from various populations, Neanderthal, and other nonhuman primates showed an miRNA, miR-1304, that carries a polymorphism on its seed region. The ancestral allele is found in Neanderthal, nonhuman primates, at low frequency (~5%) in modern Asian populations and rarely in Africans. Using miRNA target site prediction algorithms, we found that the derived allele increases the number of putative target genes for the derived miRNA more than ten-fold, indicating an important functional evolution for miR-1304. Analysis of the predicted targets for derived miR-1304 indicates an association with behavior and nervous system development and function. Two of the predicted target genes for the ancestral miR-1304 allele are important genes for teeth formation, enamelin, and amelotin. MicroRNA overexpression experiments using a luciferase-based assay showed that the ancestral version of miR-1304 reduces the enamelin- and amelotin-associated reporter gene expression by 50%, whereas the derived miR-1304 does not have any effect. Deletion of the corresponding target sites for miR-1304 in these dental genes avoided their repression, which further supports their regulation by the ancestral miR-1304. Morphological studies described several differences in the dentition of Neanderthals and present-day humans like slower dentition timing and thicker enamel for present-day humans. The observed miR-1304-mediated regulation of enamelin and amelotin could at least partially underlie these differences between the two Homo species as well as other still-unraveled phenotypic differences among modern human populations.
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Affiliation(s)
- Maria Lopez-Valenzuela
- Institut de Biologia Evolutiva, Universitat Pompeu Fabra-Consejo Superior de Investigaciones Científicas, Barcelona, Catalonia, Spain
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Masuyama T, Miyajima K, Ohshima H, Osawa M, Yokoi N, Oikawa T, Taniguchi K. A novel autosomal-recessive mutation, whitish chalk-like teeth, resembling amelogenesis imperfecta, maps to rat chromosome 14 corresponding to human 4q21. Eur J Oral Sci 2007; 113:451-6. [PMID: 16324133 DOI: 10.1111/j.1600-0722.2005.00254.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A rat mutant, whitish chalk-like teeth (wct), with white, chalk-like abnormal incisors, was discovered and morphologically and genetically characterized. The mutant rats showed tooth enamel defects that were similar to those of human amelogenesis imperfecta. The wct mutation was found to disturb the morphological transition of ameloblasts from secretory to maturation stages and to induce cyst formation. This mutation also disturbs the transfer of iron into the enamel, resulting in the whitish chalk-like incisors. A genetic linkage study indicated that the wct locus maps to a specific interval of rat chromosome 14 between D14Got13 and D14Wox2. Interestingly, the human chromosomal region orthologous to wct, a 5.5-Mb interval in human chromosome 4q21, is a critical region for the locus of human amelogenesis imperfecta AIH2. These results strongly suggest that this wct mutant is a useful model for the identification of genes responsible for amelogenesis imperfecta and molecular mechanisms of tooth development.
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Affiliation(s)
- Taku Masuyama
- Laboratory of Veterinary Anatomy, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
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Kim JW, Simmer JP, Lin BPL, Seymen F, Bartlett JD, Hu JCC. Mutational analysis of candidate genes in 24 amelogenesis imperfecta families. Eur J Oral Sci 2006; 114 Suppl 1:3-12; discussion 39-41, 379. [PMID: 16674655 DOI: 10.1111/j.1600-0722.2006.00278.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of inherited defects in dental enamel formation. The malformed enamel can be unusually thin, soft, rough and stained. The strict definition of AI includes only those cases where enamel defects occur in the absence of other symptoms. Currently, there are seven candidate genes for AI: amelogenin, enamelin, ameloblastin, tuftelin, distal-less homeobox 3, enamelysin, and kallikrein 4. To identify sequence variations in AI candidate genes in patients with isolated enamel defects, and to deduce the likely effect of each sequence variation on protein expression and structure, families with isolated enamel defects were recruited. The coding exons and nearby intron sequences were amplified for each of the AI candidate genes by using genomic DNA from the proband as template. The amplification products for the proband were sequenced. Then, other family members were tested to determine their genotype with respect to each sequence variation. All subjects received an oral examination, and intraoral photographs and dental radiographs were obtained. Out of 24 families with isolated enamel defects, only six disease-causing mutations were identified in the AI candidate genes. This finding suggests that many additional genes potentially contribute to the etiology of AI.
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Affiliation(s)
- Jung-Wook Kim
- University of Michigan School of Dentistry, University of Michigan Dental Research Laboratory, Ann Arbor, MI 48108, USA, and Department of Pediatric Dentistry & Dental Research Institute, Seoul, Korea
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Suda N, Kitahara Y, Ohyama K. A case of amelogenesis imperfecta, cleft lip and palate and polycystic kidney disease. Orthod Craniofac Res 2006; 9:52-6. [PMID: 16420275 DOI: 10.1111/j.1601-6343.2006.00337.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders characterized by developmental abnormalities of tooth enamel. The AI is also seen as part of multi-organ abnormalities, e.g. with cone-rod dystrophy, hypothalamo-hypophyseal insufficiency and renal failure. The present patient with AI and nephrocalcinosis exhibited a phenotype different from previous cases with renal failure. To highlight the characteristics of this rare case, extensive analysis that included histological, biochemical and genetic examinations was performed. PATIENT The present Japanese male patient exhibited dentition with AI and bilateral cleft lip and palate. Ground sections of his extracted tooth showed that it was hypomaturation-type AI, unlike previous cases with nephrocalcinosis were hypoplastic-type. He showed nephrocalcinosis and hematuria at 15 years of age but these symptoms appeared to be secondary to polycystic kidney disease. He showed skeletal Class II pattern with a retrognathic profile and retroclined incisors of both arches. A dolicofacial appearance was seen with an enlarged gonial angle. Biochemical makers including serum alkaline phosphatase, parathyroid hormone, calcitonin, calcium, and phosphate, were all in the normal range. Sequence analysis of the genes encoding amelogenin and enamelin, which are known to be responsible for hypoplastic-type AI, did not reveal any mutations. Since mouse null mutant of homeobox transcription factor, Msx2, exhibits a phenotype resembling AI, the human homolog of this gene, MSX2, was sequenced. There was a missense mutation of T447C that resulted in the conversion of methionine to threonine at 129.
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Affiliation(s)
- N Suda
- Maxillofacial Orthognathics, Department of Maxillofacial Reconstruction and Function, Division of Maxillofacial/Neck Reconstruction, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
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Stephanopoulos G, Garefalaki ME, Lyroudia K. Genes and related proteins involved in amelogenesis imperfecta. J Dent Res 2006; 84:1117-26. [PMID: 16304440 DOI: 10.1177/154405910508401206] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Dental enamel formation is a remarkable example of a biomineralization process. The exact mechanisms involved in this process remain partly obscure. Some of the genes encoding specific enamel proteins have been indicated as candidate genes for amelogenesis imperfecta. Mutational analyses within studied families have supported this hypothesis. Mutations in the amelogenin gene (AMELX) cause X-linked amelogenesis imperfecta, while mutations in the enamelin gene (ENAM) cause autosomal-inherited forms of amelogenesis imperfecta. Recent reports involve kallikrein-4 (KLK4), MMP-20, and DLX3 genes in the etiologies of some cases. This paper focuses mainly on the candidate genes involved in amelogenesis imperfecta and the proteins derived from them, and reviews current knowledge on their structure, localization within the tissue, and correlation with the various types of this disorder.
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Affiliation(s)
- G Stephanopoulos
- Diploma in Dental Science, Aristotle University of Thessaloniki, Greece
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Dong J, Amor D, Aldred MJ, Gu T, Escamilla M, MacDougall M. DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism. Am J Med Genet A 2005; 133A:138-41. [PMID: 15666299 DOI: 10.1002/ajmg.a.30521] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Amelogenesis imperfecta hypoplastic-hypomaturation with taurodontism (AIHHT) is an autosomal dominant (AD) trait associated with enamel defects and enlarged pulp chambers. In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease. This mutation causes a frameshift altering the last two amino acids of the DNA-binding homeodomain introducing a premature stop codon truncating the protein by 88 amino acids. This is the first report of a mutation within the homeodomain of DLX3. Previous studies have shown a DLX3 mutation outside the homeodomain associated with tricho-dento-osseous syndrome (TDO) suggesting TDO and some forms of AIHHT are allelic.
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Affiliation(s)
- Juan Dong
- Department of Pediatric Dentistry, Dental School, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC 7888, San Antonio, TX 78229, USA
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10
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Kim JW, Seymen F, Lin BPJ, Kiziltan B, Gencay K, Simmer JP, Hu JCC. ENAM mutations in autosomal-dominant amelogenesis imperfecta. J Dent Res 2005; 84:278-82. [PMID: 15723871 DOI: 10.1177/154405910508400314] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
To date, 4 unique enamelin gene (ENAM) defects have been identified in kindreds with amelogenesis imperfecta. To improve our understanding of the roles of enamelin in normal enamel formation, and to gain information related to possible genotype/phenotype correlations, we have identified 2 ENAM mutations in kindreds with hypoplastic ADAI, 1 novel (g.4806A>C, IVS6-2A>C) and 1 previously identified (g.8344delG), and have characterized the resulting enamel phenotypes. The IVS6-2A>C mutation caused a severe enamel phenotype in the proband, exhibiting horizontal grooves of severely hypoplastic enamel. The affected mother had several shallow hypoplastic horizontal grooves in the lower anterior teeth. In the case of the g.8344delG mutation, the phenotype was generalized hypoplastic enamel with shallow horizontal grooves in the middle 1/3 of the anterior teeth. In general, mutations in the human enamelin gene cause hypoplastic enamel, often with horizontal grooves, but the severity of the enamel defects is variable, even among individuals with the same mutation.
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Affiliation(s)
- J-W Kim
- Department of Orthodontics and Pediatric Dentistry, University of Michigan Dental Research Lab, 1210 Eisenhower Place, Ann Arbor, MI 48108, USA
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Rijnkels M, Elnitski L, Miller W, Rosen JM. Multispecies comparative analysis of a mammalian-specific genomic domain encoding secretory proteins. Genomics 2004; 82:417-32. [PMID: 13679022 DOI: 10.1016/s0888-7543(03)00114-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mammalian-specific casein gene cluster comprises 3 or 4 evolutionarily related genes and 1 physically linked gene with a functional association. To gain a better understanding of the mechanisms regulating the entire casein cluster at the genomic level we initiated a multispecies comparative sequence analysis. Despite the high level of divergence at the coding level, these studies have identified uncharacterized family members within two species and the presence at orthologous positions of previously uncharacterized genes. Also the previous suggestion that the histatin/statherin gene family, located in this region, was primate specific was ruled out. All 11 genes identified in this region appear to encode secretory proteins. Conservation of a number of noncoding regions was observed; one coincides with an element previously suggested to be important for beta-casein gene expression in human and cow. The conserved regions might have biological importance for the regulation of genes in this genomic "neighborhood."
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Affiliation(s)
- Monique Rijnkels
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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12
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Abstract
Dental enamel forms as a progressively thickening extracellular layer by the action of proteins secreted by ameloblasts. The most abundant enamel protein is amelogenin, which is expressed primarily from a gene on the X-chromosome (AMELX). The two most abundant non-amelogenin enamel proteins are ameloblastin and enamelin, which are expressed from the AMBN and ENAM genes, respectively. The human AMBN and ENAM genes are located on chromosome 4q13.2. The major secretory products of the human AMELX, AMBN, and ENAM genes have 175, 421, and 1103 amino acids, respectively, and are all post-translationally modified, secreted, and processed by proteases. Mutations in AMELX have been shown to cause X-linked amelogenesis imperfecta (AI), which accounts for 5% of AI cases. Mutations in ENAM cause a severe form of autosomal-dominant smooth hypoplastic AI that represents 1.5%, and a mild form of autosomal-dominant local hypoplastic AI that accounts for 27% of AI cases in Sweden. The discovery of mutations in the ENAM gene in AI kindreds proved that enamelin is critical for proper dental enamel formation and that it plays a role in human disease. Here we review how enamelin was discovered, what is known about enamelin protein structure, post-translational modifications, processing by proteases, and its potentially important functional properties such as its affinity for hydroxyapatite and influence on crystal growth in vitro. The primary structures of human, porcine, mouse, and rat enamelin are compared, and the human enamelin gene, its structure, chromosomal localization, temporal and spatial patterns of expression, and its role in the etiology of amelogenesis imperfecta are discussed.
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Affiliation(s)
- J C-C Hu
- Department of Orthodontics and Pediatric Dentistry, University of Michigan, School of Dentistry, 1011 North University, Ann Arbor, MI 48109-1078, USA.
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13
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Hart PS, Wright JT, Savage M, Kang G, Bensen JT, Gorry MC, Hart TC. Exclusion of candidate genes in two families with autosomal dominant hypocalcified amelogenesis imperfecta. Eur J Oral Sci 2003; 111:326-31. [PMID: 12887398 DOI: 10.1034/j.1600-0722.2003.00046.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The amelogenesis imperfectas (AI) are a group of hereditary enamel defects characterized by clinical and genetic diversity. The most common AI types are inherited as autosomal traits. Three mutations of the enamelin (ENAM) gene have been found in cases of autosomal dominant hypoplastic AI. The gene(s) responsible for hypocalcified forms of AI have not been identified, although a number of autosomal genes have been proposed as candidates for AI based on their expression by ameloblasts, including ameloblastin and enamelin (chromosome 4q13.3), tuftelin (chromosome 1q21), enamelysin (chromosome 11q22.3-q23) and kallikrein 4 (chromosome 19q13.3-q13.4). To localize the gene(s) responsible for autosomal dominant hypocalcified AI, we evaluated support for/against linkage of AI to genetic markers spanning five AI candidate genes in two extended families. Our data excluded all proposed candidate gene regions as causal for autosomal dominant hypocalcified AI in these families. These linkage findings provide further evidence for genetic heterogeneity among families with autosomal dominant AI and indicate that, at least, some forms of autosomal dominant hypocalcified AI are not caused by a gene in the five most commonly reported AI candidate genes.
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Affiliation(s)
- P Suzanne Hart
- Department of Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261, USA.
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14
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Downey LM, Keen TJ, Jalili IK, McHale J, Aldred MJ, Robertson SP, Mighell A, Fayle S, Wissinger B, Inglehearn CF. Identification of a locus on chromosome 2q11 at which recessive amelogenesis imperfecta and cone-rod dystrophy cosegregate. Eur J Hum Genet 2002; 10:865-9. [PMID: 12461695 DOI: 10.1038/sj.ejhg.5200884] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2002] [Revised: 08/02/2002] [Accepted: 08/13/2002] [Indexed: 11/09/2022] Open
Abstract
A consanguineous Arab pedigree in which recessive amelogenesis imperfecta (AI) and cone-rod dystrophy cosegregate, was screened for linkage to known retinal dystrophy and tooth abnormality loci by genotyping neighbouring microsatellite markers. This analysis resulted in linkage with a maximum lod score of 7.03 to the marker D2S2187 at the achromatopsia locus on chromosome 2q11, and haplotype analysis placed the gene(s) involved in a 2 cM/5 Mb interval between markers D2S2209 and D2S373. The CNGA3 gene, known to be involved in achromatopsia, lies in this interval but thorough analysis of its coding sequence revealed no mutation. Furthermore, affected individuals in four consanguineous recessive pedigrees with AI but without CRD were heterozygous at this locus, excluding it as a common cause of non-syndromic recessive AI. It remains to be established whether this pedigree is segregating two closely linked mutations causing disparate phenotypes or whether a single defect is causing pathology in both teeth and eyes.
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Affiliation(s)
- Louise M Downey
- Molecular Medicine Unit, CSB, St James's University Hospital, Leeds University, Leeds LS9 7TF UK
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15
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Kida M, Ariga T, Shirakawa T, Oguchi H, Sakiyama Y. Autosomal-dominant hypoplastic form of amelogenesis imperfecta caused by an enamelin gene mutation at the exon-intron boundary. J Dent Res 2002; 81:738-42. [PMID: 12407086 DOI: 10.1177/0810738] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Amelogenesis imperfecta (AI) is currently classified into 14 distinct subtypes based on various phenotypic criteria; however, the gene responsible for each phenotype has not been defined. We performed molecular genetic studies on a Japanese family with a possible autosomal-dominant form of AI. Previous studies have mapped an autosomal-dominant human AI locus to chromosome 4q11-q21, where two candidate genes, ameloblastin and enamelin, are located. We studied AI patients in this family, focusing on these genes, and found a mutation in the enamelin gene. The mutation detected was a heterozygous, single-G deletion within a series of 7 G residues at the exon 9-intron 9 boundary of the enamelin gene. The mutation was detected only in AI patients in the family and was not detected in other unaffected family members or control individuals. The male proband and his brother showed hypoplastic enamel in both their deciduous and permanent teeth, and their father showed local hypoplastic defects in the enamel of his permanent teeth. The clinical phenotype of these patients is similar to that of the first report of AI caused by an enamelin gene mutation. Thus, heterogeneous mutations in the enamelin gene are responsible for an autosomal-dominant hypoplastic form of AI.
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Affiliation(s)
- M Kida
- Research Group of Human Gene Therapy, Hokkaido University Graduate School of Medicine, N-15, W-7, Kita-ku, Sapporo, 060-8638, Hokkaido, Japan
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16
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Rijnkels M. Multispecies comparison of the casein gene loci and evolution of casein gene family. J Mammary Gland Biol Neoplasia 2002; 7:327-45. [PMID: 12751895 DOI: 10.1023/a:1022808918013] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Caseins, the major milk proteins, are present in a genomic cluster spanning 250-350 kb. The divergence at the coding level between human, rodent, and cattle sequences is rather extensive for most of the genes in this region. Nevertheless, comparative analysis of genomic sequences harboring the casein gene cluster region of these species (with equal evolutionary distances 79-88 Myr) shows that the organization and orientation of the genes is highly conserved. The conserved gene structure indicates that the molecular diversity of the casein genes is achieved through variable use of exons in different species and high evolutionary divergence. Comparative analysis also revealed the presence within two species of uncharacterized casein family members and ruled out the previously held notion that another gene family, located in this region, is primate-specific. Several other new genes as well as conserved noncoding sequences with potential regulatory functions were identified. All genes identified in this region are, or are predicted to be, secreted proteins involved in mineral homeostasis, nutrition, and/or host defense, and are mostly expressed in the mammary and/or salivary glands. These observations suggest a possible common ancestry for the genes in this region.
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Affiliation(s)
- Monique Rijnkels
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
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17
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Hu JC, Sun X, Zhang C, Simmer JP. A comparison of enamelin and amelogenin expression in developing mouse molars. Eur J Oral Sci 2001; 109:125-32. [PMID: 11347656 DOI: 10.1034/j.1600-0722.2001.00998.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Amelogenin and enamelin are structural proteins in the enamel matrix of developing teeth. The temporal and spatial patterns of enamelin expression in developing mouse molars have not been characterized, while controversy remains with respect to amelogenin expression by odontoblasts and cementoblasts. Here we report the results of in situ hybridization analyses of amelogenin and enamelin expression in mouse molars from postnatal days 1, 2, 3, 7, 9, 14, and 21. Amelogenin and enamelin mRNA in maxillary first molars was first observed in pre-ameloblasts on the cusp slopes at day 2. The onsets of amelogenin and enamelin expression were approximately synchronous with the initial accumulation of predentin matrix. Both proteins were expressed by ameloblasts throughout the secretory, transition, and early maturation stages. Enamelin expression terminated in maturation stage ameloblasts on day 9, while amelogenin expression is still detected in maturation stage ameloblasts on day 14. No amelogenin expression was observed in day 21 mouse molars. Amelogenin and enamelin RNA messages were restricted to ameloblasts. No expression was observed in pulp, bone, or along the developing root. We conclude that amelogenin and enamelin are enamel-specific and do not directly participate in the formation of dentin or cementum in developing mouse molars.
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Affiliation(s)
- J C Hu
- University of Texas Health Science Center at San Antonio, 78229-3900, USA
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Hu JC, Zhang CH, Yang Y, Kärrman-Mårdh C, Forsman-Semb K, Simmer JP. Cloning and characterization of the mouse and human enamelin genes. J Dent Res 2001; 80:898-902. [PMID: 11379892 DOI: 10.1177/00220345010800031001] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Enamelin is likely to be essential for proper dental enamel formation. It is secreted by ameloblasts throughout the secretory stage and can readily be isolated from the enamel matrix of developing teeth. The gene encoding human enamelin is located on the long arm of chromosome 4, in a region previously linked to an autosomal-dominant form of amelogenesis imperfecta (AI). To gain information on the structure of the enamelin gene and to facilitate the future assessment of the role of enamelin in normal and diseased enamel formation, we have cloned and characterized the mouse and human enamelin genes. Both genes are about 25 kilobases long. The enamelin gene has 10 exons interrupted by 9 introns. Translation initiates in exon 3 and terminates in exon 10. All of the intron/exon junctions within the mouse and human enamelin coding regions are between codons, so there are no partial codons in any exon, and deletion of one or more coding exons by alternative RNA splicing would not shift the downstream reading frame.
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Affiliation(s)
- J C Hu
- University of Texas Health Science Center at San Antonio, School of Dentistry, Department of Pediatric Dentistry, 78229-3900, USA.
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19
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Simmons D, Gu TT, Krebsbach PH, Yamada Y, MacDougall M. Identification and characterization of a cDNA for mouse ameloblastin. Connect Tissue Res 2001; 39:3-12; discussion 63-7. [PMID: 11062984 DOI: 10.3109/03008209809023907] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ameloblastin was first identified as one of the most abundant novel transcripts from a random screening of a rat incisor cDNA library. In situ hybridization experiments have shown ameloblastin expression to be specific to ameloblasts, with highest levels in secretory and maturation stage ameloblasts and cells of the epithelial root sheath. Ameloblastin has been identified as a candidate gene for the local hypoplastic form of autosomal dominant amelogenesis imperfecta, by virtue of it's location within the critical disease locus. The purpose of this study was to isolate a full length mouse ameloblastin cDNA and determine its temporal expression pattern during odontogenesis. A newborn mouse molar cDNA library was screened using a rat ameloblastin cDNA probe. Positive clones were confirmed by PCR analysis with ameloblastin-specific primers, and their size determined with vector-specific primers. Phage clones were rescued to phagemid using Exassist helper phage and the nucleotide sequence determined. We report here the identification of two clones, exhibiting alternative splicing of the putative open reading frame, and use of multiple polyadenylation signals. Nucleotide sequence analysis indicated a high degree of similarity to rat ameloblastin, rat amelin 1 and 2 and porcine sheathlin. Reverse transcriptase-PCR analysis using mouse first and second mandibular molar mRNA indicated initial expression at E-14. This is one day after the initial expression of tuftelin (E-13) and one day prior to that of amelogenin (E-15).
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Affiliation(s)
- D Simmons
- University of Texas Health Science Center at San Antonio, Dental School, USA
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Mårdh CK, Bäckman B, Simmons D, Golovleva I, Gu TT, Holmgren G, MacDougall M, Forsman-Semb K. Human ameloblastin gene: genomic organization and mutation analysis in amelogenesis imperfecta patients. Eur J Oral Sci 2001; 109:8-13. [PMID: 11330937 DOI: 10.1034/j.1600-0722.2001.00979.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A gene encoding the enamel protein ameloblastin (AMBN) was recently localized to a region on chromosome 4q21 containing a gene for the inherited enamel defect local hypoplastic amelogenesis imperfecta (AIH2). Ameloblastin protein is located at the Tomes processes of secretory ameloblasts and in the sheath space between rod-interrod enamel, and the AMBN gene therefore represents a viable candidate gene for local hypoplastic amelogenesis imperfecta (AI). In this study, the genomic organization of human AMBN was characterized. The gene was shown to consist of 13 exons and 12 introns. An alternatively spliced 45 bp sequence was shown not to represent a separate exon and is most likely spliced by the use of a cryptic splice site. The finding that there were no recombinations between an intragenic microsatellite and AIH2 encouraged us to evaluate this gene's potential role as a candidate gene for local hypoplastic AI. Mutation screening was performed on all 13 exons in 20 families and 8 sporadic cases with 6 different forms of AI. DNA variants were found but none that was associated exclusively with local hypoplastic AI or any of the other variants of AI in the identified Swedish families. This study excludes the coding regions and the splice sites of AMBN from a causative role in the pathogenesis of AIH2.
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Affiliation(s)
- C K Mårdh
- Department of Clinical Genetics, University Hospital, Umeå, Sweden.
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Hu CC, Hart TC, Dupont BR, Chen JJ, Sun X, Qian Q, Zhang CH, Jiang H, Mattern VL, Wright JT, Simmer JP. Cloning human enamelin cDNA, chromosomal localization, and analysis of expression during tooth development. J Dent Res 2000; 79:912-9. [PMID: 10831092 DOI: 10.1177/00220345000790040501] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Enamelin is the largest protein in the enamel matrix of developing teeth. In the pig, enamelin is secreted as 186-kDa phosphorylated glycoprotein, which is rapidly processed by enamel proteinases into smaller cleavage products. During the secretory stage of enamel formation, enamelin is found among the crystallites in the rod and interrod enamel and comprises roughly 5% of total matrix protein. Although the function of enamelin is unknown, it is thought to participate in enamel crystal nucleation and extension, and the regulation of crystal habit. Here we report the results of enamelin in situ hybridization in a day 1 mouse developing incisor that shows that enamelin is expressed by ameloblasts, but not by odontoblasts or other cells in the dental pulp. The restricted pattern of enamelin expression makes the human enamelin gene a prime candidate in the etiology of amelogenesis imperfecta (AI), a genetic disease in which defects of enamel formation occur in the absence of non-dental symptoms. We have cloned and characterized a full-length human enamelin cDNA and determined by radiation hybrid mapping and fluorescent in situ hybridization (FISH) that the gene is located on chromosome 4q near the ameloblastin gene in a region previously linked to local hypoplastic AI in six families. These findings will facilitate the search for specific mutations in the enamelin gene in kindreds suffering from amelogenesis imperfecta.
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Affiliation(s)
- C C Hu
- University of Texas Health Science Center at San Antonio, School of Dentistry, Department of Pediatric Dentistry, 78284-7888, USA.
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22
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Song YH, Naumova AK, Liebhaber SA, Cooke NE. Physical and Meiotic Mapping of the Region of Human Chromosome 4q11–q13 Encompassing the Vitamin D Binding Protein DBP/Gc-Globulin and Albumin Multigene Cluster. Genome Res 1999. [DOI: 10.1101/gr.9.6.581] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The vitamin D binding protein/Gc-globulin (DBP) gene is a member of a multigene cluster that includes albumin (ALB), α-fetoprotein (AFP), and α-albumin/afamin (AFM). All four genes have structural and functional similarities and map to the same chromosomal regions in humans (4q11–q13), mice, and rats. An accurate physical map of the region encompassing these genes is a prerequisite for study of their respective transcriptional regulation and identification of potential shared regulatory elements. By refining the physical and meiotic maps of the 4q11–q13 region and creating a local PAC contig, the order and transcriptional orientations of these four genes were determined to be centromere–3′-DBP-5′–5′-ALB-3′–5′-AFP-3′–5′-AFM3′–telomere. The ancestral DBP gene was separated from the ALBgene by >1.5 Mb. This organization and spacing establishes a foundation for ongoing functional studies in this region.
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23
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Michaels L, Lee K, Manuja S, Soucek S. Family with low-grade neuroendocrine carcinoma of salivary glands, severe sensorineural hearing loss, and enamel hypoplasia. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19990319)83:3<183::aid-ajmg7>3.0.co;2-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
This paper describes the clinical, histological and genetic findings in individuals with amelogenesis imperfecta diagnosed in more than 50 families in the county of Västerbotten, northern Sweden. Using pedigree analysis, families with autosomal and X-linked inheritance as well as sporadic cases of amelogenesis imperfecta have been recognized. A clinical subclassification in eight different variants of amelogenesis imperfecta has been made. The gene defects have been identified for two of these variants and the chromosomal location has been established for a third variant.
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Affiliation(s)
- B Bäckman
- Department of Pedodontics, Faculty of Odontology, Umeå University, Sweden
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Kärrman C, Bäckman B, Holmgren G, Forsman K. Genetic heterogeneity of autosomal dominant amelogenesis imperfecta demonstrated by its exclusion from the AIH2 region on human chromosome 4Q. Arch Oral Biol 1996; 41:893-900. [PMID: 9022927 DOI: 10.1016/s0003-9969(96)00010-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Amelogenesis imperfecta (AI) is a group of hereditary enamel defects, characterized by large clinical diversity. On the basis of differences in clinical manifestation and inheritance pattern, 14 different subtypes have been recognized. A locus for autosomal dominant AI (ADAI) of local hypoplastic type was recently mapped to the region between D4S392 and D4S395 on the long arm of chromosome 4. To test whether the chromosome 4 locus is responsible for other forms of AI as well, a linkage study was carried out with 17 families representing at least five clinical forms of ADAI. Admixture tests for heterogeneity performed with the marker D4S2456 gave statistical support for genetic heterogeneity of ADAI with the odds 78:1. Linkage to the ADAI locus on chromosome 4q (AIH2) could only be demonstrated with families expressing the local hypoplastic type, and there was no support for heterogeneity within that group of families. Furthermore, linkage could be excluded for five families with other clinical forms of ADAI. The data therefore demonstrated that ADAI is genetically heterogeneous, and that at least two loci for it exist.
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Affiliation(s)
- C Kärrman
- Department of Clinical Genetics, University Hospital, Umeå, Sweden
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