51
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Kim YJ, Kang J, Seymen F, Koruyucu M, Gencay K, Shin TJ, Hyun HK, Lee ZH, Hu JCC, Simmer JP, Kim JW. Analyses of MMP20 Missense Mutations in Two Families with Hypomaturation Amelogenesis Imperfecta. Front Physiol 2017; 8:229. [PMID: 28473773 PMCID: PMC5397402 DOI: 10.3389/fphys.2017.00229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/31/2017] [Indexed: 11/25/2022] Open
Abstract
Amelogenesis imperfecta is a group of rare inherited disorders that affect tooth enamel formation, quantitatively and/or qualitatively. The aim of this study was to identify the genetic etiologies of two families presenting with hypomaturation amelogenesis imperfecta. DNA was isolated from peripheral blood samples obtained from participating family members. Whole exome sequencing was performed using DNA samples from the two probands. Sequencing data was aligned to the NCBI human reference genome (NCBI build 37.2, hg19) and sequence variations were annotated with the dbSNP build 138. Mutations in MMP20 were identified in both probands. A homozygous missense mutation (c.678T>A; p.His226Gln) was identified in the consanguineous Family 1. Compound heterozygous MMP20 mutations (c.540T>A, p.Tyr180* and c.389C>T, p.Thr130Ile) were identified in the non-consanguineous Family 2. Affected persons in Family 1 showed hypomaturation AI with dark brown discoloration, which is similar to the clinical phenotype in a previous report with the same mutation. However, the dentition of the Family 2 proband exhibited slight yellowish discoloration with reduced transparency. Functional analysis showed that the p.Thr130Ile mutant protein had reduced activity of MMP20, while there was no functional MMP20 in the Family 1 proband. These results expand the mutational spectrum of the MMP20 and broaden our understanding of genotype-phenotype correlations in amelogenesis imperfecta.
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Affiliation(s)
- Youn Jung Kim
- Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Jenny Kang
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Figen Seymen
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Mine Koruyucu
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Koray Gencay
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Teo Jeon Shin
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Hong-Keun Hyun
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Zang Hee Lee
- Department of Cell and Developmental Biology and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, USA
| | - Jung-Wook Kim
- Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea.,Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
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52
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Eckstein M, Vaeth M, Fornai C, Vinu M, Bromage TG, Nurbaeva MK, Sorge JL, Coelho PG, Idaghdour Y, Feske S, Lacruz RS. Store-operated Ca 2+ entry controls ameloblast cell function and enamel development. JCI Insight 2017; 2:e91166. [PMID: 28352661 DOI: 10.1172/jci.insight.91166] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Loss-of-function mutations in stromal interaction molecule 1 (STIM1) impair the activation of Ca2+ release-activated Ca2+ (CRAC) channels and store-operated Ca2+ entry (SOCE), resulting in a disease syndrome called CRAC channelopathy that is characterized by severe dental enamel defects. The cause of these enamel defects has remained unclear given a lack of animal models. We generated Stim1/2K14cre mice to delete STIM1 and its homolog STIM2 in enamel cells. These mice showed impaired SOCE in enamel cells. Enamel in Stim1/2K14cre mice was hypomineralized with decreased Ca content, mechanically weak, and thinner. The morphology of SOCE-deficient ameloblasts was altered, showing loss of the typical ruffled border, resulting in mislocalized mitochondria. Global gene expression analysis of SOCE-deficient ameloblasts revealed strong dysregulation of several pathways. ER stress genes associated with the unfolded protein response were increased in Stim1/2-deficient cells, whereas the expression of components of the glutathione system were decreased. Consistent with increased oxidative stress, we found increased ROS production, decreased mitochondrial function, and abnormal mitochondrial morphology in ameloblasts of Stim1/2K14cre mice. Collectively, these data show that loss of SOCE in enamel cells has substantial detrimental effects on gene expression, cell function, and the mineralization of dental enamel.
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Affiliation(s)
- Miriam Eckstein
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, USA
| | - Martin Vaeth
- Department of Pathology, New York University School of Medicine, New York, New York, USA
| | - Cinzia Fornai
- Department of Anthropology, University of Vienna, Vienna, Austria.,Department of Evolutionary Medicine, University of Zurich, Zurich, Switzerland
| | - Manikandan Vinu
- Biology Program, Division of Science and Mathematics, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Timothy G Bromage
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, USA.,Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, New York, USA
| | - Meerim K Nurbaeva
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, USA
| | - Jessica L Sorge
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, USA
| | - Paulo G Coelho
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, New York, USA
| | - Youssef Idaghdour
- Biology Program, Division of Science and Mathematics, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Stefan Feske
- Department of Pathology, New York University School of Medicine, New York, New York, USA
| | - Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, USA
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53
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Duverger O, Ohara T, Bible PW, Zah A, Morasso MI. DLX3-Dependent Regulation of Ion Transporters and Carbonic Anhydrases is Crucial for Enamel Mineralization. J Bone Miner Res 2017; 32:641-653. [PMID: 27760456 PMCID: PMC11025043 DOI: 10.1002/jbmr.3022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/10/2016] [Accepted: 10/14/2016] [Indexed: 12/11/2022]
Abstract
Patients with tricho-dento-osseous (TDO) syndrome, an ectodermal dysplasia caused by mutations in the homeodomain transcription factor DLX3, exhibit enamel hypoplasia and hypomineralization. Here we used a conditional knockout mouse model to investigate the developmental and molecular consequences of Dlx3 deletion in the dental epithelium in vivo. Dlx3 deletion in the dental epithelium resulted in the formation of chalky hypomineralized enamel in all teeth. Interestingly, transcriptomic analysis revealed that major enamel matrix proteins and proteases known to be involved in enamel secretion and maturation were not affected significantly by Dlx3 deletion in the enamel organ. In contrast, expression of several ion transporters and carbonic anhydrases known to play an important role in enamel pH regulation during maturation was significantly affected in enamel organs lacking DLX3. Most of these affected genes showed binding of DLX3 to their proximal promoter as evidenced by chromatin immunoprecipitation sequencing (ChIP-seq) analysis on rat enamel organ. These molecular findings were consistent with altered pH staining evidenced by disruption of characteristic pH oscillations in the enamel. Taken together, these results show that DLX3 is indispensable for the regulation of ion transporters and carbonic anhydrases during the maturation stage of amelogenesis, exerting a crucial regulatory function on pH oscillations during enamel mineralization. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Olivier Duverger
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Takahiro Ohara
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Paul W Bible
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Angela Zah
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Maria I Morasso
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA
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54
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Bronckers AL, Lyaruu DM. Magnesium, pH regulation and modulation by mouse ameloblasts exposed to fluoride. Bone 2017; 94:56-64. [PMID: 27744011 DOI: 10.1016/j.bone.2016.10.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 10/05/2016] [Accepted: 10/10/2016] [Indexed: 12/25/2022]
Abstract
Supraoptimal intake of fluoride (F) induces structural defects in forming enamel, dentin and bone and increases the risk of bone fractures. In comparison to bone and dentin is formation of enamel most sensitive to low levels of F and the degree of enamel fluorosis depends on the mouse strain. What molecular mechanism is responsible for these differences in sensitivity is unclear. Maturation ameloblasts transport bicarbonates into enamel in exchange for Cl- to buffer protons released by forming apatites. We proposed that F-enhanced mineral deposition releases excess of protons that will affect mineralization in forming enamel. In this study we tested the hypothesis that increased sensitivity to F is associated with a reduced capacity of ameloblasts to buffer acids. Quantified electron probe microanalysis showed that enamel of F-sensitive C57Bl mice contained the same levels of Cl- as enamel of F-resistant FVB mice. Enamel of C57Bl mice was less mineral dense, contained less Ca but more Mg and K. Ameloblast modulation was much more impaired than in FVB mice. In enamel of FVB mice the levels of Mg correlated negative with Ca (r=-0.57, p=0.01) and with the Ca/P molar ratio (r=-0.32, p=0.53). In moderate and high acidic enamel the correlations between Mg and Ca/P ratio were strong (r=-0.75, p=0.08) to very strong negative (r=-0.98, p=0.0020), respectively. Correlations in enamel between F and Ca were (weak) negative but between F and Ca/P very high positive (r=+0.95, p=0.003) in high acidic enamel and less positive (r=0.45, p=0.27) in moderate acidic fluorotic enamel (r=0.45, p=0.27). Similar correlations between Mg and Ca/P or F and Ca/P were found in dentin and bone of fluorotic and Cftr null mice. These data are consistent with the concept that Mg delays but F increases maturation of crystals particularly when enamel is acidic. The sensitivity of forming enamel to F likely is due to the sensitivity of pH cycling to acidification of enamel associated with F-induced release of protons.
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Affiliation(s)
- Antonius Ljj Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Amsterdam, The Netherlands.
| | - Donacian M Lyaruu
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Amsterdam, The Netherlands
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55
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Bronckers ALJJ, Jalali R, Lytton J. Reduced Protein Expression of the Na +/Ca 2++K +-Exchanger (SLC24A4) in Apical Plasma Membranes of Maturation Ameloblasts of Fluorotic Mice. Calcif Tissue Int 2017; 100:80-86. [PMID: 27752731 PMCID: PMC5215084 DOI: 10.1007/s00223-016-0197-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 10/03/2016] [Indexed: 02/07/2023]
Abstract
Exposure of forming enamel to fluoride results into formation of hypomineralized enamel. We tested whether enamel hypomineralization was caused by lower expression of the NCKX4/SLC24A4 Ca2+-transporter by ameloblasts. Three commercial antibodies against NCKX4 were tested on enamel organs of wild-type and Nckx4-null mice, one of which (a mouse monoclonal) was specific. This antibody gave a prominent staining of the apical plasma membranes of maturation ameloblasts, starting at early maturation. The layer of immuno-positive ameloblasts contained narrow gaps without immunostaining or with reduced staining. In fluorotic mouse incisors, the quantity of NCKX4 protein in ameloblasts as assessed by western blotting was not different from that in non-fluorotic ameloblasts. However, immunostaining of the apical plasma membranes of fluorotic ameloblasts was strongly reduced or absent suggesting that trafficking of NCKX4 to the apical membrane was strongly reduced. Exposure to fluoride may reduce NCKX4-mediated transport of Ca2+ by maturation stage ameloblasts which delays ameloblast modulation and reduces enamel mineralization.
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Affiliation(s)
- A L J J Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA, Amsterdam, The Netherlands.
| | - R Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA, Amsterdam, The Netherlands
| | - J Lytton
- Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4Z6, Canada
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56
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Abstract
Hypomineralization of developing enamel is associated with changes in ameloblast modulation during the maturation stage. Modulation (or pH cycling) involves the cyclic transformation of ruffle-ended (RE) ameloblasts facing slightly acidic enamel into smooth-ended (SE) ameloblasts near pH-neutral enamel. The mechanism of ameloblast modulation is not clear. Failure of ameloblasts of Cftr-null and anion exchanger 2 ( Ae2)-null mice to transport Cl- into enamel acidifies enamel, prevents modulation, and reduces mineralization. It suggests that pH regulation is critical for modulation and for completion of enamel mineralization. This report presents a review of the major types of transmembrane molecules that ameloblasts express to transport calcium to form crystals and bicarbonates to regulate pH. The type of transporter depends on the developmental stage. Modulation is proposed to be driven by the pH of enamel fluid and the compositional and/or physicochemical changes that result from increased acidity, which may turn RE ameloblasts into SE mode. Amelogenins delay outgrowth of crystals and keep the intercrystalline space open for diffusion of mineral ions into complete depth of enamel. Modulation enables stepwise removal of amelogenins from the crystal surface, their degradation, and removal from the enamel. Removal of matrix allows slow expansion of crystals. Modulation also reduces the stress that ameloblasts experience when exposed to high acid levels generated by mineral formation or by increased intracellular Ca2+. By cyclically interrupting Ca2+ transport by RE ameloblasts and their transformation into SE ameloblasts, proton production ceases shortly and enables the ameloblasts to recover. Modulation also improves enamel crystal quality by selectively dissolving immature Ca2+-poor crystals, removing impurities as Mg2+ and carbonates, and recrystallizing into more acid-resistant crystals.
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Affiliation(s)
- A L J J Bronckers
- 1 Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Amsterdam, Netherlands
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57
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Prasad MK, Laouina S, El Alloussi M, Dollfus H, Bloch-Zupan A. Amelogenesis Imperfecta: 1 Family, 2 Phenotypes, and 2 Mutated Genes. J Dent Res 2016; 95:1457-1463. [PMID: 27558265 DOI: 10.1177/0022034516663200] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous group of diseases characterized by enamel defects. The authors have identified a large consanguineous Moroccan family segregating different clinical subtypes of hypoplastic and hypomineralized AI in different individuals within the family. Using targeted next-generation sequencing, the authors identified a novel heterozygous nonsense mutation in COL17A1 (c.1873C>T, p.R625*) segregating with hypoplastic AI and a novel homozygous 8-bp deletion in C4orf26 (c.39_46del, p.Cys14Glyfs*18) segregating with hypomineralized-hypoplastic AI in this family. This study highlights the phenotypic and genotypic heterogeneity of AI that can exist even within a single consanguineous family. Furthermore, the identification of novel mutations in COL17A1 and C4orf26 and their correlation with distinct AI phenotypes can contribute to a better understanding of the pathophysiology of AI and the contribution of these genes to amelogenesis.
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Affiliation(s)
- M K Prasad
- Laboratoire de Génétique Médicale, INSERM U1112, Institut de Génétique Médicale d'Alsace, Fédération de Médecine Translationnelle de Strasbourg, Université de Strasbourg, Strasbourg, France
| | - S Laouina
- Department of Pediatric Dentistry, Faculty of Dental Medicine, Mohammed V University, Rabat, Morocco
| | - M El Alloussi
- Department of Pediatric Dentistry, Faculty of Dental Medicine, Mohammed V University, Rabat, Morocco
| | - H Dollfus
- Laboratoire de Génétique Médicale, INSERM U1112, Institut de Génétique Médicale d'Alsace, Fédération de Médecine Translationnelle de Strasbourg, Université de Strasbourg, Strasbourg, France
- Centre de Référence pour les Affections Rares en Génétique Ophtalmologique, Service de Génétique Médicale, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - A Bloch-Zupan
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
- Pôle de Médecine et Chirurgie Bucco-Dentaires, Centre de Référence des Manifestations Odontologiques des Maladies Rares, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
- Institut de Génétique et de Biologie Moléculaire and Cellulaire, CNRS UMR7104, INSERM U964, Centre Européen de Recherche en Biologie et en Médecine, Université de Strasbourg, Illkirch, France
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58
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Zhekova H, Zhao C, Schnetkamp PPM, Noskov SY. Characterization of the Cation Binding Sites in the NCKX2 Na +/Ca 2+-K + Exchanger. Biochemistry 2016; 55:6445-6455. [PMID: 27805378 DOI: 10.1021/acs.biochem.6b00591] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
NCKX1-5 are proteins involved in K+-dependent Na+/Ca2+ exchange in various signal tissues. Here we present a homology model of NCKX2 based on the crystal structure of the NCX_Mj transporter found in Methanoccocus jannaschii. Molecular dynamics simulations were performed on the resultant wild-type NCKX2 model and two mutants (D548N and D575N) loaded with either four Na+ ions or one Ca2+ ion and one K+ ion, in line with the experimentally observed transport stoichiometry. The selectivity of the active site in wild-type NCKX2 for Na+, K+, and Li+ and the electrostatic interactions of the positive Na+ ions in the negatively charged active site of wild-type NCKX2 and the two mutants were evaluated from free energy perturbation calculations. For validation of the homology model, our computational results were compared to available experimental data obtained from numerous prior functional studies. The NCKX2 homology model is in good agreement with the discussed experimental data and provides valuable insights into the structure of the active site, which is lined with acidic and polar residues. The binding of the potassium and calcium ions is accomplished via Asp 575 and 548, respectively. Mutation of these residues to Asn alters the functionality of NCKX2 because of the elimination of the favorable carboxylate-cation interactions. The knowledge obtained from the NCKX2 model can be transferred to other isoforms of the NCKX family: newly discovered pathological mutations in NCKX4 and NCKX5 affect residues that are involved in ion binding and/or transport according to our homology model.
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Affiliation(s)
- Hristina Zhekova
- Center for Molecular Simulations, Department of Biological Sciences, University of Calgary , Calgary, AB, Canada T2N 1N4
| | - Chunfeng Zhao
- Center for Molecular Simulations, Department of Biological Sciences, University of Calgary , Calgary, AB, Canada T2N 1N4
| | - Paul P M Schnetkamp
- Department of Physiology & Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary, AB T2N 4N1, Canada
| | - Sergei Yu Noskov
- Center for Molecular Simulations, Department of Biological Sciences, University of Calgary , Calgary, AB, Canada T2N 1N4
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59
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Seymen F, Kim YJ, Lee YJ, Kang J, Kim TH, Choi H, Koruyucu M, Kasimoglu Y, Tuna EB, Gencay K, Shin TJ, Hyun HK, Kim YJ, Lee SH, Lee ZH, Zhang H, Hu JCC, Simmer JP, Cho ES, Kim JW. Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta. Am J Hum Genet 2016; 99:1199-1205. [PMID: 27843125 PMCID: PMC5097978 DOI: 10.1016/j.ajhg.2016.09.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 09/26/2016] [Indexed: 11/25/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders affecting tooth enamel. The affected enamel can be hypoplastic and/or hypomineralized. In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families. Families 1, 4, and 5 were affected by the homozygous ACPT mutation c.713C>T (p.Ser238Leu), family 2 by the homozygous ACPT mutation c.331C>T (p.Arg111Cys), family 3 by the homozygous ACPT mutation c.226C>T (p.Arg76Cys), and family 6 by the compound heterozygous ACPT mutations c.382G>C (p.Ala128Pro) and 397G>A (p.Glu133Lys). Analysis of the ACPT crystal structure suggests that these mutations damaged the activity of ACPT by altering the sizes and charges of key amino acid side chains, limiting accessibility of the catalytic core, and interfering with homodimerization. Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts. The study results provide evidence for the crucial function of ACPT during amelogenesis.
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60
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Parry DA, Smith CE, El-Sayed W, Poulter JA, Shore RC, Logan CV, Mogi C, Sato K, Okajima F, Harada A, Zhang H, Koruyucu M, Seymen F, Hu JCC, Simmer JP, Ahmed M, Jafri H, Johnson CA, Inglehearn CF, Mighell AJ. Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta. Am J Hum Genet 2016; 99:984-990. [PMID: 27693231 PMCID: PMC5065684 DOI: 10.1016/j.ajhg.2016.08.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/17/2016] [Indexed: 01/11/2023] Open
Abstract
Amelogenesis is the process of dental enamel formation, leading to the deposition of the hardest tissue in the human body. This process requires the intricate regulation of ion transport and controlled changes to the pH of the developing enamel matrix. The means by which the enamel organ regulates pH during amelogenesis is largely unknown. We identified rare homozygous variants in GPR68 in three families with amelogenesis imperfecta, a genetically and phenotypically heterogeneous group of inherited conditions associated with abnormal enamel formation. Each of these homozygous variants (a large in-frame deletion, a frameshift deletion, and a missense variant) were predicted to result in loss of function. GPR68 encodes a proton-sensing G-protein-coupled receptor with sensitivity in the pH range that occurs in the developing enamel matrix during amelogenesis. Immunohistochemistry of rat mandibles confirmed localization of GPR68 in the enamel organ at all stages of amelogenesis. Our data identify a role for GPR68 as a proton sensor that is required for proper enamel formation.
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61
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Smith CEL, Murillo G, Brookes SJ, Poulter JA, Silva S, Kirkham J, Inglehearn CF, Mighell AJ. Deletion of amelotin exons 3-6 is associated with amelogenesis imperfecta. Hum Mol Genet 2016; 25:3578-3587. [PMID: 27412008 PMCID: PMC5179951 DOI: 10.1093/hmg/ddw203] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/17/2016] [Accepted: 06/21/2016] [Indexed: 11/15/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic conditions that result in defective dental enamel formation. Amelotin (AMTN) is a secreted protein thought to act as a promoter of matrix mineralization in the final stage of enamel development, and is strongly expressed, almost exclusively, in maturation stage ameloblasts. Amtn overexpression and Amtn knockout mouse models have defective enamel with no other associated phenotypes, highlighting AMTN as an excellent candidate gene for human AI. However, no AMTN mutations have yet been associated with human AI. Using whole exome sequencing, we identified an 8,678 bp heterozygous genomic deletion encompassing exons 3-6 of AMTN in a Costa Rican family segregating dominant hypomineralised AI. The deletion corresponds to an in-frame deletion of 92 amino acids, shortening the protein from 209 to 117 residues. Exfoliated primary teeth from an affected family member had enamel that was of a lower mineral density compared to control enamel and exhibited structural defects at least some of which appeared to be associated with organic material as evidenced using elemental analysis. This study demonstrates for the first time that AMTN mutations cause non-syndromic human AI and explores the human phenotype, comparing it with that of mice with disrupted Amtn function.
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Affiliation(s)
- Claire E L Smith
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK.,Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Gina Murillo
- University of Costa Rica, School of Dentistry, San Pedro, Costa Rica
| | - Steven J Brookes
- Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - James A Poulter
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Sandra Silva
- University of Costa Rica, Molecular Biology Cellular Centre (CBCM), San Pedro, Costa Rica and
| | - Jennifer Kirkham
- Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Chris F Inglehearn
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Alan J Mighell
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK, .,School of Dentistry, University of Leeds, Leeds LS2 9LU, UK
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62
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Hentschel J, Tatun D, Parkhomchuk D, Kurth I, Schimmel B, Heinrich-Weltzien R, Bertzbach S, Peters H, Beetz C. Identification of the first multi-exonic WDR72 deletion in isolated amelogenesis imperfecta, and generation of a WDR72-specific copy number screening tool. Gene 2016; 590:1-4. [PMID: 27259663 DOI: 10.1016/j.gene.2016.05.040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 05/29/2016] [Indexed: 01/18/2023]
Abstract
Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous disorder of tooth development which is due to aberrant deposition or composition of enamel. Both syndromic and isolated forms exist; they may be inherited in an X-linked, autosomal recessive, or autosomal dominant manner. WDR72 is one of ten currently known genes for recessive isolated AI; nine WDR72 mutations affecting single nucleotides have been described to date. Based on whole exome sequencing in a large consanguineous AI pedigree, we obtained evidence for presence of a multi-exonic WDR72 deletion. A home-made multiplex ligation-dependent probe amplification assay was used to confirm the aberration, to narrow its extent, and to identify heterozygous carriers. Our study extends the mutational spectrum for WDR72 to include large deletions, and supports a relevance of the previously proposed loss-of-function mechanism. It also introduces an easy-to-use and highly sensitive tool for detecting WDR72 copy number alterations.
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Affiliation(s)
- Julia Hentschel
- Institute of Human Genetics, Jena University Hospital, Jena, Germany; Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | - Dana Tatun
- Institute of Medical and Human Genetics, Charité, Universitaetsmedizin Berlin, Germany
| | - Dmitri Parkhomchuk
- Institute of Medical and Human Genetics, Charité, Universitaetsmedizin Berlin, Germany
| | - Ingo Kurth
- Institute of Human Genetics, Jena University Hospital, Jena, Germany
| | - Bettina Schimmel
- Institute of Human Genetics, Jena University Hospital, Jena, Germany
| | | | | | - Hartmut Peters
- Institute of Medical and Human Genetics, Charité, Universitaetsmedizin Berlin, Germany; ChariteVivantes GmbH, Berlin, Germany
| | - Christian Beetz
- Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Jena, Germany.
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Jalloul AH, Rogasevskaia TP, Szerencsei RT, Schnetkamp PPM. A Functional Study of Mutations in K+-dependent Na+-Ca2+ Exchangers Associated with Amelogenesis Imperfecta and Non-syndromic Oculocutaneous Albinism. J Biol Chem 2016; 291:13113-23. [PMID: 27129268 DOI: 10.1074/jbc.m116.728824] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 12/20/2022] Open
Abstract
K(+)-dependent Na(+)/Ca(2+) exchangers belong to the solute carrier 24 (SLC24A1-5) gene family of membrane transporters. Five different gene products (NCKX1-5) have been identified in humans, which play key roles in biological processes including vision, olfaction, and skin pigmentation. NCKXs are bi-directional membrane transporters that transport 1 Ca(2+)+K(+) ions in exchange for 4 Na(+) ions. Recent studies have linked mutations in the SLC24A4 (NCKX4) and SLC24A5 (NCKX5) genes to amylogenesis imperfecta (AI) and non-syndromic oculocutaneous albinism (OCA6), respectively. Here, we introduced mutations found in patients with AI and OCA6 into human SLC24A4 (NCKX4) cDNA leading to single residue substitutions in the mutant NCKX4 proteins. We measured NCKX-mediated Ca(2+) transport activity of WT and mutant NCKX4 proteins expressed in HEK293 cells. Three mutant NCKX4 cDNAs represent mutations found in the SCL24A4 gene and three represent mutations found in the SCL24A5 gene involving residues conserved between NCKX4 and NCKX5. Five mutant proteins had no observable NCKX activity, whereas one mutation resulted in a 78% reduction in transport activity. Total protein expression and trafficking to the plasma membrane (the latter with one exception) were not affected in the HEK293 cell expression system. We also analyzed two mutations in a Drosophila NCKX gene that have been reported to result in an increased susceptibility for seizures, and found that both resulted in mutant proteins with significantly reduced but observable NCKX activity. The data presented here support the genetic analyses that mutations in SLC24A4 and SLC24A5 are responsible for the phenotypic defects observed in human patients.
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Affiliation(s)
- Ali H Jalloul
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Tatiana P Rogasevskaia
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Robert T Szerencsei
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Paul P M Schnetkamp
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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64
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Prasad MK, Geoffroy V, Vicaire S, Jost B, Dumas M, Le Gras S, Switala M, Gasse B, Laugel-Haushalter V, Paschaki M, Leheup B, Droz D, Dalstein A, Loing A, Grollemund B, Muller-Bolla M, Lopez-Cazaux S, Minoux M, Jung S, Obry F, Vogt V, Davideau JL, Davit-Beal T, Kaiser AS, Moog U, Richard B, Morrier JJ, Duprez JP, Odent S, Bailleul-Forestier I, Rousset MM, Merametdijan L, Toutain A, Joseph C, Giuliano F, Dahlet JC, Courval A, El Alloussi M, Laouina S, Soskin S, Guffon N, Dieux A, Doray B, Feierabend S, Ginglinger E, Fournier B, de la Dure Molla M, Alembik Y, Tardieu C, Clauss F, Berdal A, Stoetzel C, Manière MC, Dollfus H, Bloch-Zupan A. A targeted next-generation sequencing assay for the molecular diagnosis of genetic disorders with orodental involvement. J Med Genet 2016; 53:98-110. [PMID: 26502894 PMCID: PMC4752661 DOI: 10.1136/jmedgenet-2015-103302] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2015] [Revised: 09/08/2015] [Accepted: 09/24/2015] [Indexed: 11/23/2022]
Abstract
BACKGROUND Orodental diseases include several clinically and genetically heterogeneous disorders that can present in isolation or as part of a genetic syndrome. Due to the vast number of genes implicated in these disorders, establishing a molecular diagnosis can be challenging. We aimed to develop a targeted next-generation sequencing (NGS) assay to diagnose mutations and potentially identify novel genes mutated in this group of disorders. METHODS We designed an NGS gene panel that targets 585 known and candidate genes in orodental disease. We screened a cohort of 101 unrelated patients without a molecular diagnosis referred to the Reference Centre for Oro-Dental Manifestations of Rare Diseases, Strasbourg, France, for a variety of orodental disorders including isolated and syndromic amelogenesis imperfecta (AI), isolated and syndromic selective tooth agenesis (STHAG), isolated and syndromic dentinogenesis imperfecta, isolated dentin dysplasia, otodental dysplasia and primary failure of tooth eruption. RESULTS We discovered 21 novel pathogenic variants and identified the causative mutation in 39 unrelated patients in known genes (overall diagnostic rate: 39%). Among the largest subcohorts of patients with isolated AI (50 unrelated patients) and isolated STHAG (21 unrelated patients), we had a definitive diagnosis in 14 (27%) and 15 cases (71%), respectively. Surprisingly, COL17A1 mutations accounted for the majority of autosomal-dominant AI cases. CONCLUSIONS We have developed a novel targeted NGS assay for the efficient molecular diagnosis of a wide variety of orodental diseases. Furthermore, our panel will contribute to better understanding the contribution of these genes to orodental disease. TRIAL REGISTRATION NUMBERS NCT01746121 and NCT02397824.
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Affiliation(s)
- Megana K Prasad
- Laboratoire de Génétique Médicale, INSERMU1112, Institut de génétique médicale d'Alsace, FMTS, Université de Strasbourg, Strasbourg, France
| | - Véronique Geoffroy
- Laboratoire de Génétique Médicale, INSERMU1112, Institut de génétique médicale d'Alsace, FMTS, Université de Strasbourg, Strasbourg, France
| | - Serge Vicaire
- Plateforme de Biopuces et Séquençage, Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964, Université de Strasbourg, Illkirch, France
| | - Bernard Jost
- Plateforme de Biopuces et Séquençage, Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964, Université de Strasbourg, Illkirch, France
| | - Michael Dumas
- Plateforme de Biopuces et Séquençage, Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964, Université de Strasbourg, Illkirch, France
| | - Stéphanie Le Gras
- Plateforme de Biopuces et Séquençage, Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964, Université de Strasbourg, Illkirch, France
| | - Marzena Switala
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Barbara Gasse
- Evolution et Développement du Squelette-EDS, UMR7138-SAE, Université Pierre et Marie Curie, Paris, France
| | - Virginie Laugel-Haushalter
- Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964 Université de Strasbourg, Illkirch, France
| | - Marie Paschaki
- Laboratoire de Génétique Médicale, INSERMU1112, Institut de génétique médicale d'Alsace, FMTS, Université de Strasbourg, Strasbourg, France
- Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964 Université de Strasbourg, Illkirch, France
| | - Bruno Leheup
- Faculté de Médecine, CHU de Nancy, Université de Lorraine, Vandoeuvre-Les-Nancy, France
| | | | | | - Adeline Loing
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
| | - Bruno Grollemund
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Michèle Muller-Bolla
- Départment d'Odontologie Pédiatrique, UFR d'Odontologie, Université de Nice Sophia-Antipolis, CHU de Nice, Nice, France
- URB2i—EA 4462, Paris Descartes, Paris, France
| | - Séréna Lopez-Cazaux
- Faculté de Chirurgie Dentaire, Département d'Odontologie Pédiatrique, CHU Hotel Dieu, Service d'odontologie conservatrice et pédiatrique, Nantes, France
| | - Maryline Minoux
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Sophie Jung
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Frédéric Obry
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Vincent Vogt
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Jean-Luc Davideau
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Tiphaine Davit-Beal
- Evolution et Développement du Squelette-EDS, UMR7138-SAE, Université Pierre et Marie Curie, Paris, France
- Faculté de Chirurgie Dentaire, Département d'Odontologie Pédiatrique, Université Paris Descartes, Montrouge, France
| | | | - Ute Moog
- Institute of Human Genetics, Heidelberg University, Heidelberg, Germany
| | - Béatrice Richard
- Service de Consultations et Traitements Dentaires, Hospices Civils de Lyon, Faculté d'Odontologie, Université Claude Bernard Lyon1, Lyon, France
| | - Jean-Jacques Morrier
- Service de Consultations et Traitements Dentaires, Hospices Civils de Lyon, Faculté d'Odontologie, Université Claude Bernard Lyon1, Lyon, France
| | - Jean-Pierre Duprez
- Service de Consultations et Traitements Dentaires, Hospices Civils de Lyon, Faculté d'Odontologie, Université Claude Bernard Lyon1, Lyon, France
| | - Sylvie Odent
- Service de Génétique Clinique, CHU de Rennes, Rennes, France
| | - Isabelle Bailleul-Forestier
- Faculté de Chirurgie Dentaire, CHU de Toulouse, Odontologie Pédiatrique, Université Paul Sabatier, Toulouse, France
| | - Monique Marie Rousset
- Unité Fonctionnelle d'Odontologie pédiatrique, Service d'odontologie, CHRU de Lille, Lille, France
| | - Laure Merametdijan
- Faculté de Chirurgie Dentaire, Service d'Odontologie Conservatrice et Endodontie, CHU Nantes, Université de Nantes, France
| | | | - Clara Joseph
- Départment d'Odontologie Pédiatrique, Université de Nice Sophia-Antipolis, CHU Nice, Nice, France
| | | | - Jean-Christophe Dahlet
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
| | - Aymeric Courval
- Pôle de Médecine et de Chirurgie Bucco-dentaire, Hôpital Civil, HUS, Strasbourg, France
| | - Mustapha El Alloussi
- Faculty of Dental Medicine, Department of Pediatric Dentistry, University Mohammed V Rabat, Morocco
| | - Samir Laouina
- Faculty of Dental Medicine, Department of Pediatric Dentistry, University Mohammed V Rabat, Morocco
| | - Sylvie Soskin
- Pédiatrie 1, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | | | - Anne Dieux
- Service de génétique clinique Guy Fontaine, Centre Hospitalier Régionale Universitaire (CHRU) de Lille, Lille, France
| | - Bérénice Doray
- Service de Génétique Médicale, CHU de Strasbourg, Strasbourg, France
| | - Stephanie Feierabend
- Klinik für Zahnerhaltungskunde und Parodontologie, Universitats Klinikum, Freiburg, Germany
| | | | - Benjamin Fournier
- Laboratoire de Physiopathologie Orale Moléculaire INSERM UMR S1138, Centre de Recherche des Cordeliers, Universités Paris-Diderot et Paris-Descartes, Paris, France
- Centre de Référence des Malformations Rares de la Face et de la Cavité Buccale MAFACE, Hôpital Rothschild, Pôle d'Odontologie, Paris, France
| | - Muriel de la Dure Molla
- Laboratoire de Physiopathologie Orale Moléculaire INSERM UMR S1138, Centre de Recherche des Cordeliers, Universités Paris-Diderot et Paris-Descartes, Paris, France
- Centre de Référence des Malformations Rares de la Face et de la Cavité Buccale MAFACE, Hôpital Rothschild, Pôle d'Odontologie, Paris, France
| | - Yves Alembik
- Service de Génétique Médicale, CHU de Strasbourg, Strasbourg, France
| | - Corinne Tardieu
- Aix-Marseille Université, UMR 7268 ADES/EFS/CNRS, APHM, Hôpital Timone, Service Odontologie, Marseille, France
| | - François Clauss
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Ariane Berdal
- Laboratoire de Physiopathologie Orale Moléculaire INSERM UMR S1138, Centre de Recherche des Cordeliers, Universités Paris-Diderot et Paris-Descartes, Paris, France
- Centre de Référence des Malformations Rares de la Face et de la Cavité Buccale MAFACE, Hôpital Rothschild, Pôle d'Odontologie, Paris, France
| | - Corinne Stoetzel
- Laboratoire de Génétique Médicale, INSERMU1112, Institut de génétique médicale d'Alsace, FMTS, Université de Strasbourg, Strasbourg, France
| | - Marie Cécile Manière
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
| | - Hélène Dollfus
- Laboratoire de Génétique Médicale, INSERMU1112, Institut de génétique médicale d'Alsace, FMTS, Université de Strasbourg, Strasbourg, France
- Service de Génétique Médicale, Centre de Référence pour les Affections Rares en Génétique Ophtalmologique, HUS, Strasbourg, France
| | - Agnès Bloch-Zupan
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Strasbourg, France
- Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France
- Institut de Génétique et de Biologie Moléculaire and Cellulaire-Centre Européen de Recherche en Biologie et en Médecine, CNRS UMR7104, INSERM U964 Université de Strasbourg, Illkirch, France
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Inactivation of C4orf26 in toothless placental mammals. Mol Phylogenet Evol 2015; 95:34-45. [PMID: 26596502 DOI: 10.1016/j.ympev.2015.11.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/22/2015] [Accepted: 11/03/2015] [Indexed: 01/11/2023]
Abstract
Previous studies have reported inactivated copies of six enamel-related genes (AMBN, AMEL, AMTN, ENAM, KLK4, MMP20) and one dentin-related gene (DSPP) in one or more toothless vertebrates and/or vertebrates with enamelless teeth, thereby providing evidence that these genes are enamel or tooth-specific with respect to their critical functions that are maintained by natural selection. Here, we employ available genome sequences for edentulous and enamelless mammals to evaluate the enamel specificity of four genes (WDR72, SLC24A4, FAM83H, C4orf26) that have been implicated in amelogenesis imperfecta, a condition in which proper enamel formation is abrogated during tooth development. Coding sequences for WDR72, SCL24A4, and FAM83H are intact in four edentulous taxa (Chinese pangolin, three baleen whales) and three taxa (aardvark, nine-banded armadillo, Hoffmann's two-toed sloth) with enamelless teeth, suggesting that these genes have critical functions beyond their involvement in tooth development. By contrast, genomic data for C4orf26 reveal inactivating mutations in pangolin and bowhead whale as well as evidence for deletion of this gene in two minke whale species. Hybridization capture of exonic regions and PCR screens provide evidence for inactivation of C4orf26 in eight additional baleen whale species. However, C4orf26 is intact in all three species with enamelless teeth that were surveyed, as well as in 95 additional mammalian species with enamel-capped teeth. Estimates of selection intensity suggest that dN/dS ratios on branches leading to taxa with enamelless teeth are similar to the dN/dS ratio on branches leading to taxa with enamel-capped teeth. Based on these results, we conclude that C4orf26 is tooth-specific, but not enamel-specific, with respect to its essential functions that are maintained by natural selection. A caveat is that an alternative splice site variant, which translates exon 3 in a different reading frame, is putatively functional in Catarrhini and may have evolved an additional role in this primate clade.
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66
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Jalloul AH, Szerencsei RT, Schnetkamp PPM. Cation dependencies and turnover rates of the human K⁺-dependent Na⁺-Ca²⁺ exchangers NCKX1, NCKX2, NCKX3 and NCKX4. Cell Calcium 2015; 59:1-11. [PMID: 26631410 DOI: 10.1016/j.ceca.2015.11.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/21/2015] [Accepted: 11/15/2015] [Indexed: 11/29/2022]
Abstract
The Solute Carrier Family 24 (SLC24) belongs to the CaCA super family of Ca(2+)/cation antiporters and codes for five different K(+)- dependent Na(+)- Ca(2+) exchangers (NCKX1-5). NCKX proteins play a critical role in Ca(2+) homeostasis in a wide variety of biological processes such as vision, olfaction, enamel formation, Melanocortin-4-receptor-dependent satiety and skin pigmentation. NCKX transcripts are widely found throughout the brain. In this study we examine the differences between NCKX1-4 in terms of cation dependencies. We measured changes to Ca(2+) influx via the reverse exchange mode while manipulating external Ca(2+) or K(+) or internal Na(+) concentrations (External Ca(2+) Dependence, External K(+) Dependence and Internal Na(+) Dependence respectively); we also looked at the effect of external Na(+)/Ca(2+) competition and 3' 4'-Dichlorobenzamil on the transport of ions in HEK 293 cell lines. A fluorescence based assay was used to determine differences in transport kinetics of the four membrane spanning exchangers using the Michaelis-Menten constant (Km). Our results show that there are no significant differences between the NCKX isoforms to explain the variation in the specific expression pattern of these exchangers.
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Affiliation(s)
- Ali H Jalloul
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Robert T Szerencsei
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Paul P M Schnetkamp
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
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Dental enamel cells express functional SOCE channels. Sci Rep 2015; 5:15803. [PMID: 26515404 PMCID: PMC4626795 DOI: 10.1038/srep15803] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 10/06/2015] [Indexed: 12/14/2022] Open
Abstract
Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.
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Abstract
Ca(2+) release-activated Ca(2+) (CRAC) channels mediate a specific form of Ca(2+) influx called store-operated Ca(2+) entry (SOCE) that contributes to the function of many cell types. CRAC channels are composed of ORAI1 proteins located in the plasma membrane, which form its ion-conducting pore. ORAI1 channels are activated by stromal interaction molecule (STIM) 1 and STIM2 located in the endoplasmic reticulum. Loss- and gain-of-function gene mutations in ORAI1 and STIM1 in human patients cause distinct disease syndromes. CRAC channelopathy is caused by loss-of-function mutations in ORAI1 and STIM1 that abolish CRAC channel function and SOCE; it is characterized by severe combined immunodeficiency (SCID)-like disease, autoimmunity, muscular hypotonia, and ectodermal dysplasia, with defects in sweat gland function and dental enamel formation. The latter defect emphasizes an important role of CRAC channels in tooth development. By contrast, autosomal dominant gain-of-function mutations in ORAI1 and STIM1 result in constitutive CRAC channel activation, SOCE, and increased intracellular Ca(2+) levels that are associated with an overlapping spectrum of diseases, including nonsyndromic tubular aggregate myopathy (TAM) and York platelet and Stormorken syndromes. The latter two syndromes are defined, besides myopathy, by thrombocytopenia, thrombopathy, and bleeding diathesis. The fact that myopathy results from both loss- and gain-of-function mutations in ORAI1 and STIM1 highlights the importance of CRAC channels for Ca(2+) homeostasis in skeletal muscle function. The cellular dysfunction and clinical disease spectrum observed in mutant patients provide important information about the molecular regulation of ORAI1 and STIM1 proteins and the role of CRAC channels in human physiology.
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Affiliation(s)
- Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York
| | - Stefan Feske
- Department of Pathology, New York University School of Medicine, New York, New York
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Bronckers ALJJ, Lyaruu D, Jalali R, Medina JF, Zandieh-Doulabi B, DenBesten PK. Ameloblast Modulation and Transport of Cl⁻, Na⁺, and K⁺ during Amelogenesis. J Dent Res 2015; 94:1740-7. [PMID: 26403673 DOI: 10.1177/0022034515606900] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Ameloblasts express transmembrane proteins for transport of mineral ions and regulation of pH in the enamel space. Two major transporters recently identified in ameloblasts are the Na(+)K(+)-dependent calcium transporter NCKX4 and the Na(+)-dependent HPO4 (2-) (Pi) cotransporter NaPi-2b. To regulate pH, ameloblasts express anion exchanger 2 (Ae2a,b), chloride channel Cftr, and amelogenins that can bind protons. Exposure to fluoride or null mutation of Cftr, Ae2a,b, or Amelx each results in formation of hypomineralized enamel. We hypothesized that enamel hypomineralization associated with disturbed pH regulation results from reduced ion transport by NCKX4 and NaPi-2b. This was tested by correlation analyses among the levels of Ca, Pi, Cl, Na, and K in forming enamel of mice with null mutation of Cftr, Ae2a,b, and Amelx, according to quantitative x-ray electron probe microanalysis. Immunohistochemistry, polymerase chain reaction analysis, and Western blotting confirmed the presence of apical NaPi-2b and Nckx4 in maturation-stage ameloblasts. In wild-type mice, K levels in enamel were negatively correlated with Ca and Cl but less negatively or even positively in fluorotic enamel. Na did not correlate with P or Ca in enamel of wild-type mice but showed strong positive correlation in fluorotic and nonfluorotic Ae2a,b- and Cftr-null enamel. In hypomineralizing enamel of all models tested, 1) Cl(-) was strongly reduced; 2) K(+) and Na(+) accumulated (Na(+) not in Amelx-null enamel); and 3) modulation was delayed or blocked. These results suggest that a Na(+)K(+)-dependent calcium transporter (likely NCKX4) and a Na(+)-dependent Pi transporter (potentially NaPi-2b) located in ruffle-ended ameloblasts operate in a coordinated way with the pH-regulating machinery to transport Ca(2+), Pi, and bicarbonate into maturation-stage enamel. Acidification and/or associated physicochemical/electrochemical changes in ion levels in enamel fluid near the apical ameloblast membrane may reduce the transport activity of mineral transporters, which results in hypomineralization.
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Affiliation(s)
- A L J J Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - D Lyaruu
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - R Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - J F Medina
- Division of Gene Therapy and Hepatology, School of Medicine/CIMA, University of Navarra, and CIBERehd, Pamplona, Spain
| | - B Zandieh-Doulabi
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - P K DenBesten
- Department of Oral Sciences, University of California, San Francisco, CA, USA
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Novel missense mutation of the FAM83H gene causes retention of amelogenin and a mild clinical phenotype of hypocalcified enamel. Arch Oral Biol 2015; 60:1356-67. [DOI: 10.1016/j.archoralbio.2015.06.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 06/10/2015] [Accepted: 06/11/2015] [Indexed: 01/05/2023]
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71
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Varga G, Kerémi B, Bori E, Földes A. Function and repair of dental enamel - Potential role of epithelial transport processes of ameloblasts. Pancreatology 2015; 15:S55-60. [PMID: 25747281 DOI: 10.1016/j.pan.2015.01.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/28/2015] [Indexed: 12/11/2022]
Abstract
The hardest mammalian tissue, dental enamel is produced by ameloblasts, which are electrolyte-transporting epithelial cells. Although the end product is very different, they show many similarities to transporting epithelia of the pancreas, salivary glands and kidney. Enamel is produced in a multi-step epithelial secretory process that features biomineralization which is an interplay of secreted ameloblast specific proteins and the time-specific transport of minerals, protons and bicarbonate. First, "secretory" ameloblasts form the entire thickness of the enamel layer, but with low mineral content. Then they differentiate into "maturation" ameloblasts, which remove organic matrix from the enamel and in turn further build up hydroxyapatite crystals. The protons generated by hydroxyapatite formation need to be buffered, otherwise enamel will not attain full mineralization. Buffering requires a tight pH regulation and secretion of bicarbonate by ameloblasts. The whole process has been the focus of many immunohistochemical and gene knock-out studies, but, perhaps surprisingly, no functional data existed for mineral ion transport by ameloblasts. However, recent studies including ours provided a better insight for molecular mechanism of mineral formation. The secretory regulation is not completely known as yet, but its significance is crucial. Impairing regulation retards or prevents completion of enamel mineralization and results in the development of hypomineralized enamel that easily erodes after dental eruption. Factors that impair this function are fluoride and disruption of pH regulators. Revealing these factors may eventually lead to the treatment of enamel hypomineralization related to genetic or environmentally induced malformation.
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Affiliation(s)
- Gábor Varga
- Department of Oral Biology, Semmelweis University, Budapest, Hungary.
| | - Beáta Kerémi
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
| | - Erzsébet Bori
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
| | - Anna Földes
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
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72
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Seymen F, Park JC, Lee KE, Lee HK, Lee DS, Koruyucu M, Gencay K, Bayram M, Tuna EB, Lee ZH, Kim YJ, Kim JW. Novel MMP20 and KLK4 Mutations in Amelogenesis Imperfecta. J Dent Res 2015; 94:1063-9. [PMID: 26124219 DOI: 10.1177/0022034515590569] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In order to achieve highly mineralized tooth enamel, enamel proteinases serve the important function of removing the remaining organic matrix in the mineralization and maturation of the enamel matrix. Mutations in the kallikrein 4 (KLK4), enamelysin (MMP20), and WDR72 genes have been identified as causing hypomaturation enamel defects in an autosomal-recessive hereditary pattern. In this report, 2 consanguineous families with a hypomaturation-type enamel defect were recruited, and mutational analysis was performed to determine the molecular genetic etiology of the disease. Whole exome sequencing and autozygosity mapping identified novel homozygous mutations in the KLK4 (c.620_621delCT, p.Ser207Trpfs*38) and MMP20 (c.1054G>A, p.Glu352Lys) genes. Further analysis on the effect of the mutations on the translation, secretion, and function of KLK4 and MMP20 revealed that mutant KLK4 was degraded intracellularly and became inactive while mutant MMP20 was expressed at a normal level but secreted only minimally with proteolytic function.
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Affiliation(s)
- F Seymen
- Department of Pedodontics, Istanbul University, Istanbul, Turkey
| | - J-C Park
- Department of Cell and Developmental Biology & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - K-E Lee
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - H-K Lee
- Department of Cell and Developmental Biology & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - D-S Lee
- Department of Cell and Developmental Biology & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - M Koruyucu
- Department of Pedodontics, Istanbul University, Istanbul, Turkey
| | - K Gencay
- Department of Pedodontics, Istanbul University, Istanbul, Turkey
| | - M Bayram
- Department of Pedodontics, Istanbul University, Istanbul, Turkey
| | - E B Tuna
- Department of Pedodontics, Istanbul University, Istanbul, Turkey
| | - Z H Lee
- Department of Cell and Developmental Biology & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - Y-J Kim
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - J-W Kim
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea Department of Molecular Genetics & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
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73
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Wang SK, Hu Y, Yang J, Smith CE, Nunez SM, Richardson AS, Pal S, Samann AC, Hu JCC, Simmer JP. Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation. Mol Genet Genomic Med 2015; 3:302-19. [PMID: 26247047 PMCID: PMC4521966 DOI: 10.1002/mgg3.143] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/02/2015] [Accepted: 03/02/2015] [Indexed: 12/19/2022] Open
Abstract
Defects in WDR72 (WD repeat-containing protein 72) cause autosomal recessive hypomaturation amelogenesis imperfecta. We generated and characterized Wdr72-knockout/lacZ-knockin mice to investigate the role of WDR72 in enamel formation. In all analyses, enamel formed by Wdr72 heterozygous mice was indistinguishable from wild-type enamel. Without WDR72, enamel mineral density increased early during the maturation stage but soon arrested. The null enamel layer was only a tenth as hard as wild-type enamel and underwent rapid attrition following eruption. Despite the failure to further mineralize enamel deposited during the secretory stage, ectopic mineral formed on the enamel surface and penetrated into the overlying soft tissue. While the proteins in the enamel matrix were successfully degraded, the digestion products remained inside the enamel. Interactome analysis of WDR72 protein revealed potential interactions with clathrin-associated proteins and involvement in ameloblastic endocytosis. The maturation stage mandibular incisor enamel did not stain with methyl red, indicating that the enamel did not acidify beneath ruffle-ended ameloblasts. Attachment of maturation ameloblasts to the enamel layer was weakened, and SLC24A4, a critical ameloblast calcium transporter, did not localize appropriately along the ameloblast distal membrane. Fewer blood vessels were observed in the papillary layer supporting ameloblasts. Specific WDR72 expression by maturation stage ameloblasts explained the observation that enamel thickness and rod decussation (established during the secretory stage) are normal in the Wdr72 null mice. We conclude that WDR72 serves critical functions specifically during the maturation stage of amelogenesis and is required for both protein removal and enamel mineralization.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Jie Yang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108 ; Department of Pediatric Dentistry, School and Hospital of Stomatology, Peking University 22 South Avenue Zhongguancun, Haidian District, Beijing, 100081, China
| | - Charles E Smith
- Facility for Electron Microscopy Research, Department of Anatomy and Cell Biology and Faculty of Dentistry, McGill University 3640 University Street, Montreal, Quebec, Canada, H3A 2B2
| | - Stephanie M Nunez
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Amelia S Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Soumya Pal
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Andrew C Samann
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
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74
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Wang X, Zhao Y, Yang Y, Qin M. Novel ENAM and LAMB3 mutations in Chinese families with hypoplastic amelogenesis imperfecta. PLoS One 2015; 10:e0116514. [PMID: 25769099 PMCID: PMC4358960 DOI: 10.1371/journal.pone.0116514] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/10/2014] [Indexed: 11/18/2022] Open
Abstract
Amelogenesis imperfecta is a group of inherited diseases affecting the quality and quantity of dental enamel. To date, mutations in more than ten genes have been associated with non-syndromic amelogenesis imperfecta (AI). Among these, ENAM and LAMB3 mutations are known to be parts of the etiology of hypoplastic AI in human cases. When both alleles of LAMB3 are defective, it could cause junctional epidermolysis bullosa (JEB), while with only one mutant allele in the C-terminus of LAMB3, it could result in severe hypoplastic AI without skin fragility. We enrolled three Chinese families with hypoplastic autosomal-dominant AI. Despite the diagnosis falling into the same type, the characteristics of their enamel hypoplasia were different. Screening of ENAM and LAMB3 genes was performed by direct sequencing of genomic DNA from blood samples. Disease-causing mutations were identified and perfectly segregated with the enamel defects in three families: a 19-bp insertion mutation in the exon 7 of ENAM (c.406_407insTCAAAAAAGCCGACCACAA, p.K136Ifs*16) in Family 1, a single-base deletion mutation in the exon 5 of ENAM (c. 139delA, p. M47Cfs*11) in Family 2, and a LAMB3 nonsense mutation in the last exon (c.3466C>T, p.Q1156X) in Family 3. Our results suggest that heterozygous mutations in ENAM and LAMB3 genes can cause hypoplastic AI with markedly different phenotypes in Chinese patients. And these findings extend the mutation spectrum of both genes and can be used for mutation screening of AI in the Chinese population.
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Affiliation(s)
- Xin Wang
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China
| | - Yuming Zhao
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China
| | - Yuan Yang
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China
| | - Man Qin
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, China
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75
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Cherkaoui Jaouad I, El Alloussi M, Chafai El Alaoui S, Laarabi FZ, Lyahyai J, Sefiani A. Further evidence for causal FAM20A mutations and first case of amelogenesis imperfecta and gingival hyperplasia syndrome in Morocco: a case report. BMC Oral Health 2015; 15:14. [PMID: 25636655 PMCID: PMC4327795 DOI: 10.1186/1472-6831-15-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Accepted: 01/19/2015] [Indexed: 11/10/2022] Open
Abstract
Background Amelogenesis imperfecta represents a group of developmental conditions, clinically and genetically heterogeneous, that affect the structure and clinical appearance of enamel. Amelogenesis imperfecta occurred as an isolated trait or as part of a genetic syndrome. Recently, disease-causing mutations in the FAM20A gene were identified, in families with an autosomal recessive syndrome associating amelogenesis imperfecta and gingival fibromatosis. Case presentation We report, the first description of a Moroccan patient with amelogenesis imperfecta and gingival fibromatosis, in whom we performed Sanger sequencing of the entire coding sequence of FAM20A and identified a homozygous mutation in the FAM20A gene (c.34_35delCT), already reported in a family with this syndrome. Conclusion Our finding confirms that the mutations of FAM20A gene are causative for amelogenesis imperfecta and gingival fibromatosis and underlines the recurrent character of the c.34_35delCT in two different ethnic groups.
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Affiliation(s)
- Imane Cherkaoui Jaouad
- Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V, Rabat, Morocco. .,Département de Génétique Médicale, Institut National d'Hygiène, Rabat, Morocco.
| | - Mustapha El Alloussi
- Service d'odontologie pédiatrique, Faculté de médecine dentaire, Université Mohammed V, Rabat, Morocco.
| | - Siham Chafai El Alaoui
- Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V, Rabat, Morocco. .,Département de Génétique Médicale, Institut National d'Hygiène, Rabat, Morocco.
| | - Fatima Zahra Laarabi
- Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V, Rabat, Morocco. .,Département de Génétique Médicale, Institut National d'Hygiène, Rabat, Morocco.
| | - Jaber Lyahyai
- Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V, Rabat, Morocco.
| | - Abdelaziz Sefiani
- Centre de Génomique Humaine, Faculté de Médecine et de Pharmacie, Université Mohammed V, Rabat, Morocco. .,Département de Génétique Médicale, Institut National d'Hygiène, Rabat, Morocco.
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76
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Seymen F, Lee KE, Koruyucu M, Gencay K, Bayram M, Tuna EB, Lee ZH, Kim JW. Novel ITGB6 mutation in autosomal recessive amelogenesis imperfecta. Oral Dis 2015; 21:456-61. [PMID: 25431241 PMCID: PMC4440386 DOI: 10.1111/odi.12303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 11/18/2014] [Accepted: 11/21/2014] [Indexed: 11/30/2022]
Abstract
Objective Hereditary defects in tooth enamel formation, amelogenesis imperfecta (AI), can be non-syndromic or syndromic phenotype. Integrins are signaling proteins that mediate cell–cell and cell–extracellular matrix communication, and their involvement in tooth development is well known. The purposes of this study were to identify genetic cause of an AI family and molecular pathogenesis underlying defective enamel formation. Materials and Methods We recruited a Turkish family with isolated AI and performed mutational analyses to clarify the underlying molecular genetic etiology. Results Autozygosity mapping and exome sequencing identified a novel homozygous ITGB6 transversion mutation in exon 4 (c.517G>C, p.Gly173Arg). The glycine at this position in the middle of the βI-domain is conserved among a wide range of vertebrate orthologs and human paralogs. Clinically, the enamel was generally thin and pitted with pigmentation. Thicker enamel was noted at the cervical area of the molars. Conclusions In this study, we identified a novel homozygous ITGB6 mutation causing isolated AI, and this advances the understanding of normal and pathologic enamel development.
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Affiliation(s)
- F Seymen
- Department of Pedodontics, Faculty of Dentistry Istanbul University, Istanbul, Turkey
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77
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Hypomaturation amelogenesis imperfecta caused by a novel SLC24A4 mutation. Oral Surg Oral Med Oral Pathol Oral Radiol 2014; 119:e77-81. [PMID: 25442250 DOI: 10.1016/j.oooo.2014.09.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/27/2014] [Accepted: 09/03/2014] [Indexed: 01/22/2023]
Abstract
In this case report of autosomal recessive pigmented hypomaturation amelogenesis imperfecta (AI), we identify a novel homozygous missense mutation (g.165151 T>G; c.1317 T>G; p.Leu436 Arg) in SLC24A4, a gene encoding a potassium-dependent sodium-calcium exchanger that is critical for hardening dental enamel during tooth development.
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78
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Katsura KA, Horst JA, Chandra D, Le TQ, Nakano Y, Zhang Y, Horst OV, Zhu L, Le MH, DenBesten PK. WDR72 models of structure and function: a stage-specific regulator of enamel mineralization. Matrix Biol 2014; 38:48-58. [PMID: 25008349 PMCID: PMC4185229 DOI: 10.1016/j.matbio.2014.06.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 06/21/2014] [Accepted: 06/26/2014] [Indexed: 12/18/2022]
Abstract
Amelogenesis Imperfecta (AI) is a clinical diagnosis that encompasses a group of genetic mutations, each affecting processes involved in tooth enamel formation and thus, result in various enamel defects. The hypomaturation enamel phenotype has been described for mutations involved in the later stage of enamel formation, including Klk4, Mmp20, C4orf26, and Wdr72. Using a candidate gene approach we discovered a novel Wdr72 human mutation in association with AI to be a 5-base pair deletion (c.806_810delGGCAG; p.G255VfsX294). To gain insight into the function of WDR72, we used computer modeling of the full-length human WDR72 protein structure and found that the predicted N-terminal sequence forms two beta-propeller folds with an alpha-solenoid tail at the C-terminus. This domain iteration is characteristic of vesicle coat proteins, such as beta'-COP, suggesting a role for WDR72 in the formation of membrane deformation complexes to regulate intracellular trafficking. Our Wdr72 knockout mouse model (Wdr72(-/-)), containing a LacZ reporter knock-in, exhibited hypomineralized enamel similar to the AI phenotype observed in humans with Wdr72 mutations. MicroCT scans of Wdr72(-/-) mandibles affirmed the hypomineralized enamel phenotype occurring at the onset of the maturation stage. H&E staining revealed a shortened height phenotype in the Wdr72(-/-) ameloblasts with retained proteins in the enamel matrix during maturation stage. H(+)/Cl(-) exchange transporter 5 (CLC5), an early endosome acidifier, was co-localized with WDR72 in maturation-stage ameloblasts and decreased in Wdr72(-/-) maturation-stage ameloblasts. There were no obvious differences in RAB4A and LAMP1 immunostaining of Wdr72(-/-) mice as compared to wildtype controls. Moreover, Wdr72(-/-) ameloblasts had reduced amelogenin immunoreactivity, suggesting defects in amelogenin fragment resorption from the matrix. These data demonstrate that WDR72 has a major role in enamel mineralization, most notably during the maturation stage, and suggest a function involving endocytic vesicle trafficking, possibly in the removal of amelogenin proteins.
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Affiliation(s)
- K A Katsura
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - J A Horst
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - D Chandra
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - T Q Le
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - Y Nakano
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - Y Zhang
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - O V Horst
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - L Zhu
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - M H Le
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
| | - P K DenBesten
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California, San Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0422, USA
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79
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Seymen F, Lee KE, Koruyucu M, Gencay K, Bayram M, Tuna EB, Lee ZH, Kim JW. ENAM mutations with incomplete penetrance. J Dent Res 2014; 93:988-92. [PMID: 25143514 DOI: 10.1177/0022034514548222] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a genetic disease affecting tooth enamel formation. AI can be an isolated entity or a phenotype of syndromes. To date, more than 10 genes have been associated with various forms of AI. We have identified 2 unrelated Turkish families with hypoplastic AI and performed mutational analysis. Whole-exome sequencing identified 2 novel heterozygous nonsense mutations in the ENAM gene (c.454G>T p.Glu152* in family 1, c.358C>T p.Gln120* in family 2) in the probands. Affected individuals were heterozygous for the mutation in each family. Segregation analysis within each family revealed individuals with incomplete penetrance or extremely mild enamel phenotype, in spite of having the same mutation with the other affected individuals. We believe that these findings will broaden our understanding of the clinical phenotype of AI caused by ENAM mutations.
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Affiliation(s)
- F Seymen
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - K-E Lee
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - M Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - K Gencay
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - M Bayram
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - E B Tuna
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - Z H Lee
- Department of Cell and Developmental Biology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - J-W Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
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80
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Cho ES, Kim KJ, Lee KE, Lee EJ, Yun CY, Lee MJ, Shin TJ, Hyun HK, Kim YJ, Lee SH, Jung HS, Lee ZH, Kim JW. Alteration of conserved alternative splicing in AMELX causes enamel defects. J Dent Res 2014; 93:980-7. [PMID: 25117480 DOI: 10.1177/0022034514547272] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Tooth enamel is the most highly mineralized tissue in vertebrates. Enamel crystal formation and elongation should be well controlled to achieve an exceptional hardness and a compact microstructure. Enamel matrix calcification occurs with several matrix proteins, such as amelogenin, enamelin, and ameloblastin. Among them, amelogenin is the most abundant enamel matrix protein, and multiple isoforms resulting from extensive but well-conserved alternative splicing and postsecretional processing have been identified. In this report, we recruited a family with a unique enamel defect and identified a silent mutation in exon 4 of the AMELX gene. We show that the mutation caused the inclusion of exon 4, which is almost always skipped, in the mRNA transcript. We further show, by generating and characterizing a transgenic animal model, that the alteration of the ratio and quantity of the developmentally conserved alternative splicing repertoire of AMELX caused defects in enamel matrix mineralization.
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Affiliation(s)
- E S Cho
- Cluster for Craniofacial Development and Regeneration Research, Institute of Oral Biosciences, School of Dentistry, Chonbuk National University, Jeonju, Korea
| | - K-J Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - K-E Lee
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - E-J Lee
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - C Y Yun
- Cluster for Craniofacial Development and Regeneration Research, Institute of Oral Biosciences, School of Dentistry, Chonbuk National University, Jeonju, Korea
| | - M-J Lee
- Division in Anatomy and Developmental Biology, Department of Oral Biology, College of Dentistry, Yonsei University, Seoul, Korea
| | - T J Shin
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - H-K Hyun
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - Y-J Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - S-H Lee
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - H-S Jung
- Division in Anatomy and Developmental Biology, Department of Oral Biology, College of Dentistry, Yonsei University, Seoul, Korea
| | - Z H Lee
- Department of Cell and Developmental Biology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - J-W Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
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81
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Li XF, Lytton J. An essential role for the K+-dependent Na+/Ca2+-exchanger, NCKX4, in melanocortin-4-receptor-dependent satiety. J Biol Chem 2014; 289:25445-59. [PMID: 25096581 DOI: 10.1074/jbc.m114.564450] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
K(+)-dependent Na(+)/Ca(2+)-exchangers are broadly expressed in various tissues, and particularly enriched in neurons of the brain. The distinct physiological roles for the different members of this Ca(2+) transporter family are, however, not well described. Here we show that gene-targeted mice lacking the K(+)-dependent Na(+)/Ca(2+)-exchanger, NCKX4 (gene slc24a4 or Nckx4), display a remarkable anorexia with severe hypophagia and weight loss. Feeding and satiety are coordinated centrally by melanocortin-4 receptors (MC4R) in neurons of the hypothalamic paraventricular nucleus (PVN). The hypophagic response of Nckx4 knock-out mice is accompanied by hyperactivation of neurons in the PVN, evidenced by high levels of c-Fos expression. The activation of PVN neurons in both fasted Nckx4 knock-out and glucose-injected wild-type animals is blocked by Ca(2+) removal and MC4R antagonists. In cultured hypothalamic neurons, melanocyte stimulating hormone induces an MC4R-dependent and sustained Ca(2+) signal, which requires phospholipase C activity and plasma membrane Ca(2+) entry. The Ca(2+) signal is enhanced in hypothalamic neurons from Nckx4 knock-out animals, and is depressed in cells in which NCKX4 is overexpressed. Finally, MC4R-dependent oxytocin expression in the PVN, a key essential step in satiety, is prevented by blocking phospholipase C activation or Ca(2+) entry. These findings highlight an essential, and to our knowledge previously unknown, role for Ca(2+) signaling in the MC4R pathway that leads to satiety, and a novel non-redundant role for NCKX4-mediated Ca(2+) extrusion in controlling MC4R signaling and feeding behavior. Together, these findings highlight a novel pathway that potentially could be exploited to develop much needed new therapeutics to tackle eating disorders and obesity.
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Affiliation(s)
- Xiao-Fang Li
- From the Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4Z6, Canada
| | - Jonathan Lytton
- From the Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4Z6, Canada
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82
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Simmer JP, Richardson AS, Wang SK, Reid BM, Bai Y, Hu Y, Hu JCC. Ameloblast transcriptome changes from secretory to maturation stages. Connect Tissue Res 2014; 55 Suppl 1:29-32. [PMID: 25158176 PMCID: PMC4252044 DOI: 10.3109/03008207.2014.923862] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 12/11/2013] [Accepted: 12/11/2013] [Indexed: 02/03/2023]
Abstract
The purpose of this study was to identify the major molecular components in the secretory and maturation stages of amelogenesis through transcriptome analyses. Ameloblasts (40 sections per age group) were laser micro-dissected from Day 5 (secretory stage) and Days 11-12 (maturation stage) first molars. PolyA+ RNA was isolated from the lysed cells, converted to cDNA, and amplified to generate a cDNA library. DNA sequences were obtained using next generation sequencing and analyzed to identify genes whose expression had increased or decreased at least 1.5-fold in maturation stage relative to secretory stage ameloblasts. Among the 9198 genes that surpassed the quality threshold, 373 showed higher expression in secretory stage, while 614 genes increased in maturation stage ameloblasts. The results were cross-checked against a previously published transcriptome generated from tissues overlying secretory and maturation stage mouse incisor enamel and 34 increasing and 26 decreasing expressers common to the two studies were identified. Expression of F2r, which encodes protease activated receptor 1 (PAR1) that showed 10-fold higher expression during the secretory stage in our transcriptome analysis, was characterized in mouse incisors by immunohistochemistry. PAR1 was detected in secretory, but not maturation stage ameloblasts. We conclude that transcriptome analyses are a good starting point for identifying genes/proteins that are critical for proper dental enamel formation and that PAR1 is specifically expressed by secretory stage ameloblasts.
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Affiliation(s)
- James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Amelia S. Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Bryan M. Reid
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Yongsheng Bai
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI, USA
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI, USA
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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83
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Wang S, Choi M, Richardson AS, Reid BM, Seymen F, Yildirim M, Tuna E, Gençay K, Simmer JP, Hu JC. STIM1 and SLC24A4 Are Critical for Enamel Maturation. J Dent Res 2014; 93:94S-100S. [PMID: 24621671 PMCID: PMC4107542 DOI: 10.1177/0022034514527971] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Dental enamel formation depends upon the transcellular transport of Ca(2+) by ameloblasts, but little is known about the molecular mechanism, or even if the same process is operative during the secretory and maturation stages of amelogenesis. Identifying mutations in genes involved in Ca(2+) homeostasis that cause inherited enamel defects can provide insights into the molecular participants and potential mechanisms of Ca(2+) handling by ameloblasts. Stromal Interaction Molecule 1 (STIM1) is an ER transmembrane protein that activates membrane-specific Ca(2+) influx in response to the depletion of ER Ca(2+) stores. Solute carrier family 24, member 4 (SLC24A4), is a Na(+)/K(+)/Ca(2+) transporter that exchanges intracellular Ca(2+) and K(+) for extracellular Na(+). We identified a proband with syndromic hypomaturation enamel defects caused by a homozygous C to T transition (g.232598C>T c.1276C>T p.Arg426Cys) in STIM1, and a proband with isolated hypomaturation enamel defects caused by a homozygous C to T transition (g.124552C>T; c.437C>T; p.Ala146Val) in SLC24A4. Immunohistochemistry of developing mouse molars and incisors showed positive STIM1 and SLC24A4 signal specifically in maturation-stage ameloblasts. We conclude that enamel maturation is dependent upon STIM1 and SLC24A4 function, and that there are important differences in the Ca(2+) transcellular transport systems used by secretory- and maturation-stage ameloblasts.
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Affiliation(s)
- S Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA Oral Health Sciences Program, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, USA
| | - M Choi
- Department of Biomedical Sciences, College of Medicine, Seoul National University, 275-1 Yongon-dong, Chongno-gu, Seoul 110-768, Korea Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, USA
| | - A S Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - B M Reid
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - F Seymen
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - M Yildirim
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - E Tuna
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - K Gençay
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - J P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - J C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
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84
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Poulter JA, Murillo G, Brookes SJ, Smith CEL, Parry DA, Silva S, Kirkham J, Inglehearn CF, Mighell AJ. Deletion of ameloblastin exon 6 is associated with amelogenesis imperfecta. Hum Mol Genet 2014; 23:5317-24. [PMID: 24858907 PMCID: PMC4168819 DOI: 10.1093/hmg/ddu247] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Amelogenesis imperfecta (AI) describes a heterogeneous group of inherited dental enamel defects reflecting failure of normal amelogenesis. Ameloblastin (AMBN) is the second most abundant enamel matrix protein expressed during amelogenesis. The pivotal role of AMBN in amelogenesis has been confirmed experimentally using mouse models. However, no AMBN mutations have been associated with human AI. Using autozygosity mapping and exome sequencing, we identified genomic deletion of AMBN exon 6 in a second cousin consanguineous family with three of the six children having hypoplastic AI. The genomic deletion corresponds to an in-frame deletion of 79 amino acids, shortening the protein from 447 to 368 residues. Exfoliated primary teeth (unmatched to genotype) were available from family members. The most severely affected had thin, aprismatic enamel (similar to that reported in mice homozygous for Ambn lacking exons 5 and 6). Other teeth exhibited thicker but largely aprismatic enamel. One tooth had apparently normal enamel. It has been suggested that AMBN may function in bone development. No clinically obvious bone or other co-segregating health problems were identified in the family investigated. This study confirms for the first time that AMBN mutations cause non-syndromic human AI and that mouse models with disrupted Ambn function are valid.
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Affiliation(s)
- James A Poulter
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | | | | | - Claire E L Smith
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - David A Parry
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Sandra Silva
- Biology, Molecular Cellular Centre (CBCM), University of Costa Rica, San Pedro, Costa Rica
| | | | - Chris F Inglehearn
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Alan J Mighell
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK School of Dentistry, University of Leeds, Leeds LS2 9LU, UK
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85
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Rosenthal SL, Kamboh MI. Late-Onset Alzheimer's Disease Genes and the Potentially Implicated Pathways. CURRENT GENETIC MEDICINE REPORTS 2014; 2:85-101. [PMID: 24829845 PMCID: PMC4013444 DOI: 10.1007/s40142-014-0034-x] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Late-onset Alzheimer's disease (LOAD) is a devastating neurodegenerative disease with no effective treatment or cure. In addition to APOE, recent large genome-wide association studies have identified variation in over 20 loci that contribute to disease risk: CR1, BIN1, INPP5D, MEF2C, TREM2, CD2AP, HLA-DRB1/HLA-DRB5, EPHA1, NME8, ZCWPW1, CLU, PTK2B, PICALM, SORL1, CELF1, MS4A4/MS4A6E, SLC24A4/RIN3,FERMT2, CD33, ABCA7, CASS4. In addition, rare variants associated with LOAD have also been identified in APP, TREM2 and PLD3 genes. Previous research has identified inflammatory response, lipid metabolism and homeostasis, and endocytosis as the likely modes through which these gene products participate in Alzheimer's disease. Despite the clustering of these genes across a few common pathways, many of their roles in disease pathogenesis have yet to be determined. In this review, we examine both general and postulated disease functions of these genes and consider a comprehensive view of their potential roles in LOAD risk.
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Affiliation(s)
- Samantha L. Rosenthal
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261 USA
| | - M. Ilyas Kamboh
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261 USA
- Alzheimer’s Disease Research Center, University of Pittsburgh, Pittsburgh, PA USA
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86
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Seymen F, Lee KE, Tran Le C, Yildirim M, Gencay K, Lee Z, Kim JW. Exonal Deletion of SLC24A4 Causes Hypomaturation Amelogenesis Imperfecta. J Dent Res 2014; 93:366-70. [DOI: 10.1177/0022034514523786] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Amelogenesis imperfecta is a heterogeneous group of genetic conditions affecting enamel formation. Recently, mutations in solute carrier family 24 member 4 ( SLC24A4) have been identified to cause autosomal recessive hypomaturation amelogenesis imperfecta. We recruited a consanguineous family with hypomaturation amelogenesis imperfecta with generalized brown discoloration. Sequencing of the candidate genes identified a 10-kb deletion, including exons 15, 16, and most of the last exon of the SLC24A4 gene. Interestingly, this deletion was caused by homologous recombination between two 354-bp-long homologous sequences located in intron 14 and the 3′ UTR. This is the first report of exonal deletion in SLC24A4 providing confirmatory evidence that the function of SLC24A4 in calcium transport has a crucial role in the maturation stage of amelogenesis.
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Affiliation(s)
- F. Seymen
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - K.-E. Lee
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - C.G. Tran Le
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - M. Yildirim
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - K. Gencay
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - Z.H. Lee
- Department of Cell and Developmental Biology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - J.-W. Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
- Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
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87
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Purinergic stimulation of K+-dependent Na+/Ca2+ exchanger isoform 4 requires dual activation by PKC and CaMKII. Biosci Rep 2013; 33:BSR20130099. [PMID: 24224486 PMCID: PMC3867797 DOI: 10.1042/bsr20130099] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
K+-dependent Na+/Ca2+-exchanger isoform 4 (NCXK4) is one of the most broadly expressed members of the NCKX (K+-dependent Na+/Ca2+-exchanger) family. Recent data indicate that NCKX4 plays a critical role in controlling normal Ca2+ signal dynamics in olfactory and other neurons. Synaptic Ca2+ dynamics are modulated by purinergic regulation, mediated by ATP released from synaptic vesicles or from neighbouring glial cells. Previous studies have focused on modulation of Ca2+ entry pathways that initiate signalling. Here we have investigated purinergic regulation of NCKX4, a powerful extrusion pathway that assists in terminating Ca2+ signals. NCKX4 activity was stimulated by ATP through activation of the P2Y receptor signalling pathway. Stimulation required dual activation of PKC (protein kinase C) and CaMKII (Ca2+/calmodulin-dependent protein kinase II). Mutating T312, a putative PKC phosphorylation site on NCKX4, partially prevented purinergic stimulation. These data illustrate how purinergic regulation can shape the dynamics of Ca2+ signalling by activating a signal damping and termination pathway. Activity of the K+-dependent Na+/Ca2+-exchanger, NCKX4, is stimulated by purinergic signals that depend on dual activation of two protein kinase pathways. This regulation provides a novel mechanism to shape Ca2+ signaling and thus to have important impact on neuronal processes.
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88
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Poulter JA, Brookes SJ, Shore RC, Smith CEL, Abi Farraj L, Kirkham J, Inglehearn CF, Mighell AJ. A missense mutation in ITGB6 causes pitted hypomineralized amelogenesis imperfecta. Hum Mol Genet 2013; 23:2189-97. [PMID: 24319098 PMCID: PMC3959822 DOI: 10.1093/hmg/ddt616] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We identified a family in which pitted hypomineralized amelogenesis imperfecta (AI) with premature enamel failure segregated in an autosomal recessive fashion. Whole-exome sequencing revealed a missense mutation (c.586C>A, p.P196T) in the I-domain of integrin-β6 (ITGB6), which is consistently predicted to be pathogenic by all available programmes and is the only variant that segregates with the disease phenotype. Furthermore, a recent study revealed that mice lacking a functional allele of Itgb6 display a hypomaturation AI phenotype. Phenotypic characterization of affected human teeth in this study showed areas of abnormal prismatic organization, areas of low mineral density and severe abnormal surface pitting in the tooth's coronal portion. We suggest that the pathogenesis of this form of AI may be due to ineffective ligand binding of ITGB6 resulting in either compromised cell-matrix interaction or compromised ITGB6 activation of transforming growth factor-β (TGF-β) impacting indirectly on ameloblast-ameloblast interactions and proteolytic processing of extracellular matrix proteins via MMP20. This study adds to the list of genes mutated in AI and further highlights the importance of cell-matrix interactions during enamel formation.
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Affiliation(s)
- James A Poulter
- Leeds Institutes of Molecular Medicine, University of Leeds, Leeds LS9 7TF, UK
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89
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Wang SK, Choi M, Richardson AS, Reid BM, Lin BP, Wang SJ, Kim JW, Simmer JP, Hu JCC. ITGB6 loss-of-function mutations cause autosomal recessive amelogenesis imperfecta. Hum Mol Genet 2013; 23:2157-63. [PMID: 24305999 DOI: 10.1093/hmg/ddt611] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Integrins are cell-surface adhesion receptors that bind to extracellular matrices (ECM) and mediate cell-ECM interactions. Some integrins are known to play critical roles in dental enamel formation. We recruited two Hispanic families with generalized hypoplastic amelogenesis imperfecta (AI). Analysis of whole-exome sequences identified three integrin beta 6 (ITGB6) mutations responsible for their enamel malformations. The female proband of Family 1 was a compound heterozygote with an ITGB6 transition mutation in Exon 4 (g.4545G > A c.427G > A p.Ala143Thr) and an ITGB6 transversion mutation in Exon 6 (g.27415T > A c.825T > A p.His275Gln). The male proband of Family 2 was homozygous for an ITGB6 transition mutation in Exon 11 (g.73664C > T c.1846C > T p.Arg616*) and hemizygous for a transition mutation in Exon 6 of Nance-Horan Syndrome (NHS Xp22.13; g.355444T > C c.1697T > C p.Met566Thr). These are the first disease-causing ITGB6 mutations to be reported. Immunohistochemistry of mouse mandibular incisors localized ITGB6 to the distal membrane of differentiating ameloblasts and pre-ameloblasts, and then ITGB6 appeared to be internalized by secretory stage ameloblasts. ITGB6 expression was strongest in the maturation stage and its localization was associated with ameloblast modulation. Our findings demonstrate that early and late amelogenesis depend upon cell-matrix interactions. Our approach (from knockout mouse phenotype to human disease) demonstrates the power of mouse reverse genetics in mutational analysis of human genetic disorders and attests to the need for a careful dental phenotyping in large-scale knockout mouse projects.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI 48108, USA
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90
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Bartlett JD. Dental enamel development: proteinases and their enamel matrix substrates. ISRN DENTISTRY 2013; 2013:684607. [PMID: 24159389 PMCID: PMC3789414 DOI: 10.1155/2013/684607] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 07/15/2013] [Indexed: 12/31/2022]
Abstract
This review focuses on recent discoveries and delves in detail about what is known about each of the proteins (amelogenin, ameloblastin, and enamelin) and proteinases (matrix metalloproteinase-20 and kallikrein-related peptidase-4) that are secreted into the enamel matrix. After an overview of enamel development, this review focuses on these enamel proteins by describing their nomenclature, tissue expression, functions, proteinase activation, and proteinase substrate specificity. These proteins and their respective null mice and human mutations are also evaluated to shed light on the mechanisms that cause nonsyndromic enamel malformations termed amelogenesis imperfecta. Pertinent controversies are addressed. For example, do any of these proteins have a critical function in addition to their role in enamel development? Does amelogenin initiate crystallite growth, does it inhibit crystallite growth in width and thickness, or does it do neither? Detailed examination of the null mouse literature provides unmistakable clues and/or answers to these questions, and this data is thoroughly analyzed. Striking conclusions from this analysis reveal that widely held paradigms of enamel formation are inadequate. The final section of this review weaves the recent data into a plausible new mechanism by which these enamel matrix proteins support and promote enamel development.
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Affiliation(s)
- John D. Bartlett
- Harvard School of Dental Medicine & Chair, Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge MA 02142, USA
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