1
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Loss of biological control of enamel mineralization in amelogenin-phosphorylation-deficient mice. J Struct Biol 2022; 214:107844. [DOI: 10.1016/j.jsb.2022.107844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 02/18/2022] [Accepted: 02/22/2022] [Indexed: 11/23/2022]
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2
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Huang Y, Bai Y, Chang C, Bacino M, Cheng IC, Li L, Habelitz S, Li W, Zhang Y. A N-Terminus Domain Determines Amelogenin's Stability to Guide the Development of Mouse Enamel Matrix. J Bone Miner Res 2021; 36:1781-1795. [PMID: 33957008 PMCID: PMC9307086 DOI: 10.1002/jbmr.4329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 04/25/2021] [Accepted: 04/29/2021] [Indexed: 12/16/2022]
Abstract
Amelogenins, the principal proteins in the developing enamel microenvironment, self-assemble into supramolecular structures to govern the remodeling of a proteinaceous organic matrix into longitudinally ordered hydroxyapatite nanocrystal arrays. Extensive in vitro studies using purified native or recombinant proteins have revealed the potential of N-terminal amelogenin on protein self-assembly and its ability to guide the mineral deposition. We have previously identified a 14-aa domain (P2) of N-terminal amelogenin that can self-assemble into amyloid-like fibrils in vitro. Here, we investigated how this domain affects the ability of amelogenin self-assembling and stability of enamel matrix protein scaffolding in an in vivo animal model. Mice harboring mutant amelogenin lacking P2 domain had a hypoplastic, hypomineralized, and aprismatic enamel. In vitro, the mutant recombinant amelogenin without P2 had a reduced tendency to self-assemble and was prone to accelerated hydrolysis by MMP20, the prevailing metalloproteinase in early developing enamel matrix. A reduced amount of amelogenins and a lack of elongated fibrous assemblies in the development enamel matrix of mutant mice were evident compared with that in the wild-type mouse enamel matrix. Our study is the first to demonstrate that a subdomain (P2) at the N-terminus of amelogenin controls amelogenin's assembly into a transient protein scaffold that resists rapid proteolysis during enamel development in an animal model. Understanding the building blocks of fibrous scaffold that guides the longitudinal growth of hydroxyapatites in enamel matrix sheds light on protein-mediated enamel bioengineering. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Yulei Huang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA.,Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, USA
| | - Yushi Bai
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Chih Chang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Margot Bacino
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Ieong Cheng Cheng
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Li Li
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Stefan Habelitz
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Wu Li
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Yan Zhang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
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3
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Wang J, Liu Z, Ren B, Wang Q, Wu J, Yang N, Sui X, Li L, Li M, Zhang X, Li X, Wang B. Biomimetic mineralisation systems for in situ enamel restoration inspired by amelogenesis. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2021; 32:115. [PMID: 34455518 PMCID: PMC8403113 DOI: 10.1007/s10856-021-06583-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 07/05/2021] [Indexed: 05/28/2023]
Abstract
Caries and dental erosion are common oral diseases. Traditional treatments involve the mechanical removal of decay and filling but these methods are not suitable for cases involving large-scale enamel erosion, such as hypoplasia. To develop a noninvasive treatment, promoting remineralisation in the early stage of caries is of considerable clinical significance. Therefore, biomimetic mineralisation is an ideal approach for restoring enamel. Biomimetic mineralisation forms a new mineral layer that is tightly attached to the surface of the enamel. This review details the state-of-art achievements on the application of amelogenin and non-amelogenin, amorphous calcium phosphate, ions flow and other techniques in the biomimetic mineralisation of enamel. The ultimate goal of this review was to shed light on the requirements for enamel biomineralisation. Hence, herein, we summarise two strategies of biological minimisation systems for in situ enamel restoration inspired by amelogenesis that have been developed in recent years and compare their advantages and disadvantages.
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Affiliation(s)
- Jue Wang
- Department of Obsterics and Gynecology, The Second Hospital of Jilin University, Changchun, Jilin, China
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Zhihui Liu
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Bingyu Ren
- Department of Thyroid surgery, The Second Hospital of Jilin University, Changchun, Jilin, China
| | - Qian Wang
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Jia Wu
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Nan Yang
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Xin Sui
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Lingfeng Li
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Meihui Li
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Xiao Zhang
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Xinyue Li
- Department of Prosthodontics, Hospital of Stomatology, Jilin University, Changchun, Jilin, China
| | - Bowei Wang
- Department of Obsterics and Gynecology, The Second Hospital of Jilin University, Changchun, Jilin, China.
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4
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Habelitz S, Bai Y. Mechanisms of Enamel Mineralization Guided by Amelogenin Nanoribbons. J Dent Res 2021; 100:1434-1443. [PMID: 34009057 DOI: 10.1177/00220345211012925] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The nanofibrous nature and its intricate structural organization are the basis for the extraordinary ability of sound enamel to outlive masticatory forces at minimal failure rates. Apatite nanofibers of several hundreds of micrometers to possibly millimeters in length originate during the secretory stage of amelogenesis as 2-nm-thin and 15-nm-wide ribbons that develop and grow in length under the guidance of a dynamic mixture of specialized proteins, the developing enamel matrix (DEM). A critical role in the unidirectional and oriented growth of enamel mineral ribbons has been attributed to amelogenin, the major constituent of the DEM. This review elaborates on recent studies on the ability of ribbon-like assemblies of amelogenin to template the formation of an amorphous calcium phosphate precursor that transforms into apatite mineral ribbons similar to the ones observed in developing enamel. A mechanistic model of the biological processes that drive biomineralization in enamel is presented in the context of a comparative analysis of enamel mouse models and earlier structural data of the DEM emphasizing a regulatory role of the matrix metalloproteinase 20 in mineral deposition and the involvement of a process-directing agent for the templated mineral growth directed by amelogenin nanoribbons.
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Affiliation(s)
- S Habelitz
- Department of Preventative and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, CA, USA
| | - Y Bai
- Department of Preventative and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, CA, USA
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5
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Petronijevic S, Stig S, Halstensen TS. Epitope mapping of anti-amelogenin IgG in untreated celiac children. Eur J Oral Sci 2021; 129:e12770. [PMID: 33656197 DOI: 10.1111/eos.12770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/04/2021] [Accepted: 01/12/2021] [Indexed: 11/28/2022]
Abstract
Children with untreated celiac disease (CeD) may develop enamel defects, and children with severe CeD have significantly increased levels of IgG to amelogenin, which may interfere with normal amelogenesis depending on which epitope(s) they bind. Children with untreated CeD (n = 42), for whom CeD had been confirmed either by biopsy (n = 17, cohort 1) or by the presence of particularly high serum levels of anti-transglutaminase 2 (TG2) IgA (n = 25, cohort 2), were selected from 146 children with CeD, and 10 controls were selected from 34 children who did not have CeD. Samples from these 52 children were used for detailed IgG anti-amelogenin, X isoform (AMELX) epitope mapping using 31 overlapping, 10-22mer peptides in ELISA. Although sera from both groups showed reactivity to peptides containing sequences from the N and C terminus of AMELX, sera from children with CeD reacted more strongly to peptides from the central region (amino acids 75-150) containing both a binding site for transforming growth factor-β (TGF-β), as well as the enzymatic cleavage sites for matrix metalloproteinase-20 and for kallikrein-4. Antigen-specific extraction revealed that only IgG to the central region cross-reacted to gliadin. Thus, cross-reactive anti-gliadin/amelogenin IgG may affect normal amelogenesis by interfering with enzymatic degradation, proper folding, and/or TGF-β signaling in children with untreated CeD.
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Affiliation(s)
- Sanja Petronijevic
- Institute of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Solveig Stig
- Institute of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Trond S Halstensen
- Institute of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.,Medical Department, Lovisenberg Diaconal Hospital, Oslo, Norway
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Ahuja S, Surabhi K, Gandhi K, Kapoor R, Malhotra R, Kumar D. Comparative Evaluation of Success of Biodentine and Mineral Trioxide Aggregate with Formocresol as Pulpotomy Medicaments in Primary Molars: An In Vivo Study. Int J Clin Pediatr Dent 2020; 13:167-173. [PMID: 32742096 PMCID: PMC7366755 DOI: 10.5005/jp-journals-10005-1740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Aim The study was designed to evaluate and compare the success of Biodentine and mineral trioxide aggregate (MTA) in comparison to formocresol as pulpotomy medicaments over 9 months of the follow-up period. Materials and methods The sample of 60 deciduous molars of patients aged 4–7 years were incorporated in the study. The molars were randomly allocated to the experimental and control groups. Following coronal pulp removal and achieving hemostasis, the radicular pulp was covered with either Biodentine or MTA (experimental groups). In the control group, a cotton pellet soaked with diluted formocresol (one-fifth dilution of Buckley's formocresol) was placed over the radicular pulp for 1 minute. All pulpotomized molars were later restored with stainless steel crowns (SSCs). Results The achieved clinical success over 9 months of the follow-up period was 100, 95, and 70% with Biodentine, MTA, and formocresol, respectively. The achieved radiographic success over 9 months of the follow-up period was 95, 60, and 25% with Biodentine, MTA, and formocresol, respectively. Conclusion Favorable biological, physical, mechanical, and good manipulation properties of Biodentine show that this material can be used efficiently as a pulpotomy medicament in the clinical practice. How to cite this article Ahuja S, Surabhi K, Gandhi K, et al. Comparative Evaluation of Success of Biodentine and Mineral Trioxide Aggregate with Formocresol as Pulpotomy Medicaments in Primary Molars: An In Vivo Study. Int J Clin Pediatr Dent 2020;13(2):167–173.
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Affiliation(s)
- Shilpa Ahuja
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
| | - Kumari Surabhi
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
| | - Kapil Gandhi
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
| | - Rishabh Kapoor
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
| | - Ritika Malhotra
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
| | - Dipanshu Kumar
- Department of Pedodontics and Preventive Dentistry, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India
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7
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Shin NY, Yamazaki H, Beniash E, Yang X, Margolis SS, Pugach MK, Simmer JP, Margolis HC. Amelogenin phosphorylation regulates tooth enamel formation by stabilizing a transient amorphous mineral precursor. J Biol Chem 2020; 295:1943-1959. [PMID: 31919099 DOI: 10.1074/jbc.ra119.010506] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/30/2019] [Indexed: 11/06/2022] Open
Abstract
Dental enamel comprises interwoven arrays of extremely long and narrow crystals of carbonated hydroxyapatite called enamel rods. Amelogenin (AMELX) is the predominant extracellular enamel matrix protein and plays an essential role in enamel formation (amelogenesis). Previously, we have demonstrated that full-length AMELX forms higher-order supramolecular assemblies that regulate ordered mineralization in vitro, as observed in enamel rods. Phosphorylation of the sole AMELX phosphorylation site (Ser-16) in vitro greatly enhances its capacity to stabilize amorphous calcium phosphate (ACP), the first mineral phase formed in developing enamel, and prevents apatitic crystal formation. To test our hypothesis that AMELX phosphorylation is critical for amelogenesis, we generated and characterized a hemizygous knockin (KI) mouse model with a phosphorylation-defective Ser-16 to Ala-16 substitution in AMELX. Using EM analysis, we demonstrate that in the absence of phosphorylated AMELX, KI enamel lacks enamel rods, the hallmark component of mammalian enamel, and, unlike WT enamel, appears to be composed of less organized arrays of shorter crystals oriented normal to the dentinoenamel junction. KI enamel also exhibited hypoplasia and numerous surface defects, whereas heterozygous enamel displayed highly variable mosaic structures with both KI and WT features. Importantly, ACP-to-apatitic crystal transformation occurred significantly faster in KI enamel. Secretory KI ameloblasts also lacked Tomes' processes, consistent with the absence of enamel rods, and underwent progressive cell pathology throughout enamel development. In conclusion, AMELX phosphorylation plays critical mechanistic roles in regulating ACP-phase transformation and enamel crystal growth, and in maintaining ameloblast integrity and function during amelogenesis.
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Affiliation(s)
- Nah-Young Shin
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - Hajime Yamazaki
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Xu Yang
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Seth S Margolis
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Megan K Pugach
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - James P Simmer
- Department of Biologic and Material Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan 48108
| | - Henry C Margolis
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Periodontics and Preventive Dentistry, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213.
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8
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Le Norcy E, Lesieur J, Sadoine J, Rochefort GY, Chaussain C, Poliard A. Phosphorylated and Non-phosphorylated Leucine Rich Amelogenin Peptide Differentially Affect Ameloblast Mineralization. Front Physiol 2018; 9:55. [PMID: 29472869 PMCID: PMC5809816 DOI: 10.3389/fphys.2018.00055] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/17/2018] [Indexed: 01/03/2023] Open
Abstract
The Leucine Rich Amelogenin Peptide (LRAP) is a product of alternative splicing of the amelogenin gene. As full length amelogenin, LRAP has been shown, in precipitation experiments, to regulate hydroxyapatite (HAP) crystal formation depending on its phosphorylation status. However, very few studies have questioned the impact of its phosphorylation status on enamel mineralization in biological models. Therefore, we have analyzed the effect of phosphorylated (+P) or non-phosphorylated (−P) LRAP on enamel formation in ameloblast-like cell lines and ex vivo cultures of murine postnatal day 1 molar germs. To this end, the mineral formed was analyzed by micro-computed tomography, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, Selected Area Electon Diffraction imaging. Amelogenin gene transcription was evaluated by qPCR analysis. Our data show that, in both cells and germ cultures, LRAP is able to induce an up-regulation of amelogenin transcription independently of its phosphorylation status. Mineral formation is promoted by LRAP(+P) in all models, while LRAP(–P) essentially affects HAP crystal formation through an increase in crystal length and organization in ameloblast-like cells. Altogether, these data suggest a differential effect of LRAP depending on its phosphorylation status and on the ameloblast stage at the time of treatment. Therefore, LRAP isoforms can be envisioned as potential candidates for treatment of enamel lesions or defects and their action should be further evaluated in pathological models.
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Affiliation(s)
- Elvire Le Norcy
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France.,APHP, Hôpital Bretonneau, Service d'Odontologie, Paris, France
| | - Julie Lesieur
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France
| | - Jeremy Sadoine
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France
| | - Gaël Y Rochefort
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France
| | - Catherine Chaussain
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France.,APHP, Hôpital Bretonneau, Service d'Odontologie, Paris, France
| | - Anne Poliard
- EA2496 Faculté de Chirurgie Dentaire, Université Paris Descartes USPC, Paris, France
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9
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Bidlack FB, Xia Y, Pugach MK. Dose-Dependent Rescue of KO Amelogenin Enamel by Transgenes in Vivo. Front Physiol 2017; 8:932. [PMID: 29201008 PMCID: PMC5696357 DOI: 10.3389/fphys.2017.00932] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 11/02/2017] [Indexed: 01/22/2023] Open
Abstract
Mice lacking amelogenin (KO) have hypoplastic enamel. Overexpression of the most abundant amelogenin splice variant M180 and LRAP transgenes can substantially improve KO enamel, but only ~40% of the incisor thickness is recovered and the prisms are not as tightly woven as in WT enamel. This implies that the compositional complexity of the enamel matrix is required for different aspects of enamel formation, such as organizational structure and thickness. The question arises, therefore, how important the ratio of different matrix components, and in particular amelogenin splice products, is in enamel formation. Can optimal expression levels of amelogenin transgenes representing both the most abundant splice variants and cleavage product at protein levels similar to that of WT improve the enamel phenotype of KO mice? Addressing this question, our objective was here to understand dosage effects of amelogenin transgenes (Tg) representing the major splice variants M180 and LRAP and cleavage product CTRNC on enamel properties. Amelogenin KO mice were mated with M180Tg, CTRNCTg and LRAPTg mice to generate M180Tg and CTRNCTg double transgene and M180Tg, CTRNCTg, LRAPTg triple transgene mice with transgene hemizygosity (on one allelle) or homozygosity (on both alleles). Transgene homo- vs. hemizygosity was determined by qPCR and relative transgene expression confirmed by Western blot. Enamel volume and mineral density were analyzed by microCT, thickness and structure by SEM, and mechanical properties by Vickers microhardness testing. There were no differences in incisor enamel thickness between amelogenin KO mice with three or two different transgenes, but mice homozygous for a given transgene had significantly thinner enamel than mice hemizygous for the transgene (p < 0.05). The presence of the LRAPTg did not improve the phenotype of M180Tg/CTRNCTg/KO enamel. In the absence of endogenous amelogenin, the addition of amelogenin transgenes representing the most abundant splice variants and cleavage product can rescue abnormal enamel properties and structure, but only up to a maximum of ~80% that of molar and ~40% that of incisor wild-type enamel.
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Affiliation(s)
- Felicitas B Bidlack
- Forsyth Institute, Cambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, United States
| | - Yan Xia
- Forsyth Institute, Cambridge, MA, United States
| | - Megan K Pugach
- Forsyth Institute, Cambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, United States
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Xiao Z, Que K, Wang H, An R, Chen Z, Qiu Z, Lin M, Song J, Yang J, Lu D, Shen M, Guan B, Wang Y, Deng X, Yang X, Cai Q, Deng J, Ma L, Zhang X, Zhang X. Rapid biomimetic remineralization of the demineralized enamel surface using nano-particles of amorphous calcium phosphate guided by chimaeric peptides. Dent Mater 2017; 33:1217-1228. [DOI: 10.1016/j.dental.2017.07.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 07/05/2017] [Accepted: 07/13/2017] [Indexed: 12/30/2022]
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11
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Pandya M, Lin T, Li L, Allen MJ, Jin T, Luan X, Diekwisch TGH. Posttranslational Amelogenin Processing and Changes in Matrix Assembly during Enamel Development. Front Physiol 2017; 8:790. [PMID: 29089900 PMCID: PMC5651044 DOI: 10.3389/fphys.2017.00790] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 09/26/2017] [Indexed: 01/20/2023] Open
Abstract
The extracellular tooth enamel matrix is a unique, protein-rich environment that provides the structural basis for the growth of long and parallel oriented enamel crystals. Here we have conducted a series of in vivo and in vitro studies to characterize the changes in matrix shape and organization that take place during the transition from ameloblast intravesicular matrices to extracellular subunit compartments and pericrystalline sheath proteins, and correlated these changes with stages of amelogenin matrix protein posttranslational processing. Our transmission electron microscopic studies revealed a 2.5-fold difference in matrix subunit compartment dimensions between secretory vesicle and extracellular enamel protein matrix as well as conformational changes in matrix structure between vesicles, stippled materials, and pericrystalline matrix. Enamel crystal growth in organ culture demonstrated granular mineral deposits associated with the enamel matrix framework, dot-like mineral deposits along elongating initial enamel crystallites, and dramatic changes in enamel matrix configuration following the onset of enamel crystal formation. Atomic force micrographs provided evidence for the presence of both linear and hexagonal/ring-shaped full-length recombinant amelogenin protein assemblies on mica surfaces, while nickel-staining of the N-terminal amelogenin N92 His-tag revealed 20 nm diameter oval and globular amelogenin assemblies in N92 amelogenin matrices. Western blot analysis comparing loosely bound and mineral-associated protein fractions of developing porcine enamel organs, superficial and deep enamel layers demonstrated (i) a single, full-length amelogenin band in the enamel organ followed by 3 kDa cleavage upon entry into the enamel layer, (ii) a close association of 8–16 kDa C-terminal amelogenin cleavage products with the growing enamel apatite crystal surface, and (iii) a remaining pool of N-terminal amelogenin fragments loosely retained between the crystalline phases of the deep enamel layer. Together, our data establish a temporo-spatial correlation between amelogenin protein processing and the changes in enamel matrix configuration that take place during the transition from intracellular vesicle compartments to extracellular matrix assemblies and the formation of protein coats along elongating apatite crystal surfaces. In conclusion, our study suggests that enzymatic cleavage of the amelogenin enamel matrix protein plays a key role in the patterning of the organic matrix framework as it affects enamel apatite crystal growth and habit.
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Affiliation(s)
- Mirali Pandya
- Texas A&M Center for Craniofacial Research and Diagnosis, Dallas, TX, United States
| | - Tiffani Lin
- UCLA School of Dentistry, Los Angeles, CA, United States.,Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago, Chicago, IL, United States
| | - Leo Li
- Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago, Chicago, IL, United States.,University of Michigan Medical School, Ann Arbor, MI, United States
| | | | - Tianquan Jin
- Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago, Chicago, IL, United States.,Biocytogen, Worcester, MA, United States
| | - Xianghong Luan
- Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago, Chicago, IL, United States
| | - Thomas G H Diekwisch
- Texas A&M Center for Craniofacial Research and Diagnosis, Dallas, TX, United States.,Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago, Chicago, IL, United States
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12
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Awada T, Kunimatsu R, Yoshimi Y, Hirose N, Mitsuyoshi T, Sumi K, Tanimoto K. Effects of C-terminal amelogenin peptides on the metabolism of osteoblasts. Biochem Biophys Res Commun 2017; 482:1154-1159. [DOI: 10.1016/j.bbrc.2016.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 12/01/2016] [Indexed: 02/02/2023]
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13
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Charone S, De Lima Leite A, Peres-Buzalaf C, Silva Fernandes M, Ferreira de Almeida L, Zardin Graeff MS, Cardoso de Oliveira R, Campanelli AP, Groisman S, Whitford GM, Everett ET, Buzalaf MAR. Proteomics of Secretory-Stage and Maturation-Stage Enamel of Genetically Distinct Mice. Caries Res 2016; 50:24-31. [DOI: 10.1159/000442301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 11/06/2015] [Indexed: 11/19/2022] Open
Abstract
The mechanisms by which excessive ingestion of fluoride (F) during amelogenesis leads to dental fluorosis (DF) are still not precisely known. Inbred strains of mice vary in their susceptibility to develop DF, and therefore permit the investigation of underlying molecular events influencing DF severity. We employed a proteomic approach to characterize and evaluate changes in protein expression from secretory-stage and maturation-stage enamel in 2 strains of mice with different susceptibilities to DF (A/J, i.e. ‘susceptible' and 129P3/J, i.e. ‘resistant'). Weanling male and female susceptible and resistant mice fed a low-F diet were divided into 2 F-water treatment groups. They received water containing 0 (control) or 50 mg F/l for 6 weeks. Plasma and incisor enamel was analyzed for F content. For proteomic analysis, the enamel proteins extracted for each group were separated by 2-dimensional electrophoresis and subsequently characterized by liquid-chromatography electrospray-ionization quadrupole time-of-flight mass spectrometry. F data were analyzed by 2-way ANOVA and Bonferroni's test (p < 0.05). Resistant mice had significantly higher plasma and enamel F concentrations when compared with susceptible mice in the F-treated groups. The proteomic results for mice treated with 0 mg F/l revealed that during the secretory stage, resistant mice had a higher abundance of proteins than their susceptible counterparts, but this was reversed during the maturation stage. Treatment with F greatly increased the number of protein spots detected in both stages. Many proteins not previously described in enamel (e.g. type 1 collagen) as well as some uncharacterized proteins were identified. Our findings reveal new insights regarding amelogenesis and how genetic background and F affect this process.
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Xia Y, Ren A, Pugach MK. Truncated amelogenin and LRAP transgenes improve Amelx null mouse enamel. Matrix Biol 2015; 52-54:198-206. [PMID: 26607574 DOI: 10.1016/j.matbio.2015.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 11/18/2015] [Accepted: 11/18/2015] [Indexed: 10/22/2022]
Abstract
Amelogenin is the most abundant enamel protein involved in enamel mineralization. Our goal was to determine whether all three regions of amelogenin (N-terminus, C-terminus, central core) are required for enamel formation. Amelogenin RNA is alternatively spliced, resulting in at least 16 different amelogenin isoforms in mice, with M180 and LRAP expressed most abundantly. Soon after secretion by ameloblasts, M180 is cleaved by MMP20 resulting in C-terminal truncated (CTRNC) amelogenin. We aimed to determine whether the 2 transgenes (Tg), LRAP and CTRNC together, can improve LRAPTg/Amelx-/- and CTRNCTg/Amelx-/- enamel thickness and prism organization, which were not rescued in Amelx-/- enamel. We generated CTRNCTg/LRAPTg/Amelx-/- mice and analyzed developing and mature incisor and molar enamel histologically, by microCT, SEM and microhardness testing. CTRNCTg and LRAPTg overexpression together significantly improved the enamel phenotype of LRAPTg/Amelx-/- and CTRNCTg/Amelx-/- mouse enamel, however enamel microhardness was recovered only when M180Tg was expressed, alone or with LRAPTg. We determined that both LRAP and CTRNC, which together express all three regions of the amelogenin protein (N-terminus, C-terminus and hydrophobic core) contribute to the final enamel thickness and prism organization in mice.
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Affiliation(s)
- Yan Xia
- Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA
| | - Anna Ren
- Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA
| | - Megan K Pugach
- Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA; Department of Developmental Biology, Harvard School of Dental Medicine, 188 Longwood Ave, Boston, MA 02115, USA.
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15
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Gopinathan G, Jin T, Liu M, Li S, Atsawasuwan P, Galang MT, Allen M, Luan X, Diekwisch TGH. The expanded amelogenin polyproline region preferentially binds to apatite versus carbonate and promotes apatite crystal elongation. Front Physiol 2014; 5:430. [PMID: 25426079 PMCID: PMC4227485 DOI: 10.3389/fphys.2014.00430] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/16/2014] [Indexed: 01/23/2023] Open
Abstract
The transition from invertebrate calcium carbonate-based calcite and aragonite exo- and endoskeletons to the calcium phosphate-based vertebrate backbones and jaws composed of microscopic hydroxyapatite crystals is one of the great revolutions in the evolution of terrestrial organisms. To identify potential factors that might have played a role in such a transition, three key domains of the vertebrate tooth enamel protein amelogenin were probed for calcium mineral/protein interactions and their ability to promote calcium phosphate and calcium carbonate crystal growth. Under calcium phosphate crystal growth conditions, only the carboxy-terminus augmented polyproline repeat peptide, but not the N-terminal peptide nor the polyproline repeat peptide alone, promoted the formation of thin and parallel crystallites resembling those of bone and initial enamel. In contrast, under calcium carbonate crystal growth conditions, all three amelogenin-derived polypeptides caused calcium carbonate to form fused crystalline conglomerates. When examined for long-term crystal growth, polyproline repeat peptides of increasing length promoted the growth of shorter calcium carbonate crystals with broader basis, contrary to the positive correlation between polyproline repeat element length and apatite mineralization published earlier. To determine whether the positive correlation between polyproline repeat element length and apatite crystal growth versus the inverse correlation between polyproline repeat length and calcium carbonate crystal growth were related to the binding affinity of the polyproline domain to either apatite or carbonate, a parallel series of calcium carbonate and calcium phosphate/apatite protein binding studies was conducted. These studies demonstrated a remarkable binding affinity between the augmented amelogenin polyproline repeat region and calcium phosphates, and almost no binding to calcium carbonates. In contrast, the amelogenin N-terminus bound to both carbonate and apatite, but preferentially to calcium carbonate. Together, these studies highlight the specific binding affinity of the augmented amelogenin polyproline repeat region to calcium phosphates versus calcium carbonate, and its unique role in the growth of thin apatite crystals as they occur in vertebrate biominerals. Our data suggest that the rise of apatite-based biominerals in vertebrates might have been facilitated by a rapid evolution of specialized polyproline repeat proteins flanked by a charged domain, resulting in apatite crystals with reduced width, increased length, and tailored biomechanical properties.
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Affiliation(s)
- Gokul Gopinathan
- Oral Biology, University of Illinois at Chicago Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
| | - Tianquan Jin
- Biocytogen, One Innovation Drive Worcester, MA, USA
| | - Min Liu
- Department of Periodontology, Stomatological Hospital, Jilin University Changchun, China
| | - Steve Li
- Oral Biology, University of Illinois at Chicago Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
| | - Phimon Atsawasuwan
- University of Illinois at Chicago Department of Orthodontics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
| | - Maria-Therese Galang
- University of Illinois at Chicago Department of Orthodontics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
| | - Michael Allen
- Department of Medicine, University of Chicago Chicago, IL, USA
| | - Xianghong Luan
- Oral Biology, University of Illinois at Chicago Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
| | - Thomas G H Diekwisch
- Oral Biology, University of Illinois at Chicago Brodie Laboratory for Craniofacial Genetics, University of Illinois at Chicago College of Dentistry Chicago, IL, USA
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16
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Pugach MK, Gibson CW. Analysis of enamel development using murine model systems: approaches and limitations. Front Physiol 2014; 5:313. [PMID: 25278900 PMCID: PMC4166228 DOI: 10.3389/fphys.2014.00313] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 08/01/2014] [Indexed: 11/24/2022] Open
Abstract
A primary goal of enamel research is to understand and potentially treat or prevent enamel defects related to amelogenesis imperfecta (AI). Rodents are ideal models to assist our understanding of how enamel is formed because they are easily genetically modified, and their continuously erupting incisors display all stages of enamel development and mineralization. While numerous methods have been developed to generate and analyze genetically modified rodent enamel, it is crucial to understand the limitations and challenges associated with these methods in order to draw appropriate conclusions that can be applied translationally, to AI patient care. We have highlighted methods involved in generating and analyzing rodent enamel and potential approaches to overcoming limitations of these methods: (1) generating transgenic, knockout, and knockin mouse models, and (2) analyzing rodent enamel mineral density and functional properties (structure and mechanics) of mature enamel. There is a need for a standardized workflow to analyze enamel phenotypes in rodent models so that investigators can compare data from different studies. These methods include analyses of gene and protein expression, developing enamel histology, enamel pigment, degree of mineralization, enamel structure, and mechanical properties. Standardization of these methods with regard to stage of enamel development and sample preparation is crucial, and ideally investigators can use correlative and complementary techniques with the understanding that developing mouse enamel is dynamic and complex.
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Affiliation(s)
- Megan K Pugach
- Department of Mineralized Tissue Biology, The Forsyth Institute, Harvard School of Dental Medicine, Harvard University Cambridge, MA, USA
| | - Carolyn W Gibson
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania Philadelphia, PA, USA
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17
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Pugach MK, Ozer F, Mulmadgi R, Li Y, Suggs C, Wright JT, Bartlett JD, Gibson CW, Lindemeyer RG. Shear bond strength of dentin and deproteinized enamel of amelogenesis imperfecta mouse incisors. Pediatr Dent 2014; 36:130-136. [PMID: 25303500 PMCID: PMC4196710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
PURPOSE The purposes of this study were to: (1) investigate adhesion through shear bond strength (SBS) testing of a resin composite bonded with a self-etching bonding system (SEB) to amelogenesis imperfecta (AI)-affected deproteinized mouse enamel or dentin; and (2) compare wild-type (WT), amelogenin null (AmelxKO), and matrix metalloproteinase-20 null (Mmp20KO) enamel and dentin phenotypes using micro-CT and nanoindentation. METHODS Enamel incisor surfaces of WT, AmelxKO, and Mmp20KO mice were treated with SEB with and without sodium hypochlorite and tested for SBS. Incisor dentin was also treated with SEB and tested for SBS. These surfaces were further examined by scanning electron miscroscopy. Micro-CT and nanoindentation analyses were performed on mouse dentin and enamel. Data were analyzed for significance by analysis of variance. RESULTS Deproteinization did not improve SBS of SEB to these AI-affected enamel surfaces. SBS of AmelxKO teeth was similar in dentin and enamel; however, it was higher in Mmp20KO dentin. The nanohardness of knockout enamel was significantly lower than WT, while knockout dentin nanohardness was not different from WT. CONCLUSIONS Using animal amelogenesis imperfecta models, enamel sodium hypochlorite deproteinization of hypoplastic and hypoplastic-hypomaturation enamel did not increase shear bond strength, while removal of the defective enamel allowed optimal dentin bonding.
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Affiliation(s)
- Megan K Pugach
- Department of Mineralized Tissue Biology, The Forsyth Institute, Cambridge, Mass., USA; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Mass., USA
| | - Fusun Ozer
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa, USA
| | - Raj Mulmadgi
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa, USA
| | - Yong Li
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa, USA
| | - Cynthia Suggs
- Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, N.C., USA
| | - J Timothy Wright
- Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, N.C., USA
| | - John D Bartlett
- Mineralized Tissue Biology, The Forsyth Institute, Cambridge, Mass., USA
| | - Carolyn W Gibson
- Department of Anatomy and Cell Biology, at the School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa, USA
| | - Rochelle G Lindemeyer
- Department of Pediatric Dentistry, at the School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa, USA.
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18
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New insights into the functions of enamel matrices in calcified tissues. JAPANESE DENTAL SCIENCE REVIEW 2014. [DOI: 10.1016/j.jdsr.2014.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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19
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Li Y, Konicki WS, Wright JT, Suggs C, Xue H, Kuehl MA, Kulkarni AB, Gibson CW. Mouse genetic background influences the dental phenotype. Cells Tissues Organs 2014; 198:448-56. [PMID: 24732779 DOI: 10.1159/000360157] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/28/2014] [Indexed: 11/19/2022] Open
Abstract
Dental enamel covers the crown of the vertebrate tooth and is considered to be the hardest tissue in the body. Enamel develops during secretion of an extracellular matrix by ameloblast cells in the tooth germ, prior to eruption of the tooth into the oral cavity. Secreted enamel proteins direct mineralization patterns during the maturation stage of amelogenesis as the tooth prepares to erupt. The amelogenins are the most abundant enamel proteins and are required for normal enamel development. Phenotypic differences were observed between incisors from individual Amelx (amelogenin) null mice that had a mixed 129xC57BL/6J genetic background and between inbred wild-type (WT) mice with different genetic backgrounds (C57BL/6J, C3H/HeJ, FVB/NJ). We hypothesized that this could be due to modifier genes, as human patients with a mutation in an enamel protein gene causing the enamel defect amelogenesis imperfecta (AI) can also have varied appearance of dentitions within a kindred. Enamel density measurements varied for all WT inbred strains midway during incisor development. Enamel thickness varied between some WT strains, and, unexpectedly, dentin density varied extensively between incisors and molars of all WT and Amelx null strains studied. WTFVB/NJ incisors were more similar to those of Amelx null mice than to those of the other WT strains in terms of incisor height/width ratio and pattern of enamel mineralization. Strain-specific differences led to the conclusion that modifier genes may be implicated in determining both normal development and severity of enamel appearance in AI mouse models and may in future studies be related to phenotypic heterogeneity within human AI kindreds reported in the literature.
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Affiliation(s)
- Yong Li
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa., USA
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20
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Pugach MK, Suggs C, Li Y, Wright JT, Kulkarni AB, Bartlett JD, Gibson CW. M180 amelogenin processed by MMP20 is sufficient for decussating murine enamel. J Dent Res 2013; 92:1118-22. [PMID: 24072097 DOI: 10.1177/0022034513506444] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Amelogenin (AMELX) and matrix metalloproteinase-20 (MMP20) are essential for proper enamel development. Amelx and Mmp20 mutations cause amelogenesis imperfecta. MMP20, a protease secreted by ameloblasts, is responsible for processing enamel proteins, including AMELX, during the secretory stage of enamel formation. Of at least 16 different amelogenin splice products, the most abundant isoform found in murine ameloblasts and developing enamel is the M180 protein. To understand the role of MMP20 processing of M180 AMELX, we generated AmelxKO/Mmp20KO (DKO) mice with an amelogenin (M180Tg) transgene. We analyzed the enamel phenotype by SEM to determine enamel structure and thickness, µCT, and by nanoindentation to quantify enamel mechanical properties. M180Tg/DKO mouse enamel had 37% of the hardness of M180Tg/AmelxKO teeth and demonstrated a complete lack of normal prismatic architecture. Although molar enamel of M180Tg/AmelxKO mice was thinner than WT, it had similar mechanical properties and decussating enamel prisms, which were abolished by the loss of MMP20 in the M180Tg/DKO mice. Retention of the C-terminus or complete lack of this domain is unable to rescue amelogenin null enamel. We conclude that among amelogenins, M180 alone is sufficient for normal enamel mechanical properties and prism patterns, but that additional amelogenin splice products are required to restore enamel thickness.
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Affiliation(s)
- M K Pugach
- Department of Anatomy and Cell Biology, University of Pennsylvania School of Dental Medicine, 240 S. 40th Street, Philadelphia, PA 19104-6030, USA
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21
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Xue H, Li Y, Everett ET, Ryan K, Peng L, Porecha R, Yan Y, Lucchese AM, Kuehl MA, Pugach MK, Bouchard J, Gibson CW. Ameloblasts require active RhoA to generate normal dental enamel. Eur J Oral Sci 2013; 121:293-302. [PMID: 23841780 DOI: 10.1111/eos.12059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2013] [Indexed: 12/20/2022]
Abstract
RhoA plays a fundamental role in regulation of the actin cytoskeleton, intercellular attachment, and cell proliferation. During amelogenesis, ameloblasts (which produce the enamel proteins) undergo dramatic cytoskeletal changes and the RhoA protein level is up-regulated. Transgenic mice were generated that express a dominant-negative RhoA transgene in ameloblasts using amelogenin gene-regulatory sequences. Transgenic and wild-type (WT) molar tooth germs were incubated with sodium fluoride (NaF) or sodium chloride (NaCl) in organ culture. Filamentous actin (F-actin) stained with phalloidin was elevated significantly in WT ameloblasts treated with NaF compared with WT ameloblasts treated with NaCl or with transgenic ameloblasts treated with NaF, thereby confirming a block in the RhoA/Rho-associated protein kinase (ROCK) pathway in the transgenic mice. Little difference in quantitative fluorescence (an estimation of fluorosis) was observed between WT and transgenic incisors from mice provided with drinking water containing NaF. We subsequently found reduced transgene expression in incisors compared with molars. Transgenic molar teeth had reduced amelogenin, E-cadherin, and Ki67 compared with WT molar teeth. Hypoplastic enamel in transgenic mice correlates with reduced expression of the enamel protein, amelogenin, and E-cadherin and cell proliferation are regulated by RhoA in other tissues. Together these findings reveal deficits in molar ameloblast function when RhoA activity is inhibited.
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Affiliation(s)
- Hui Xue
- Department of Anatomy and Cell Biology, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104, USA
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22
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CryoTEM study of effects of phosphorylation on the hierarchical assembly of porcine amelogenin and its regulation of mineralization in vitro. J Struct Biol 2013; 183:250-7. [PMID: 23707542 DOI: 10.1016/j.jsb.2013.05.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Revised: 04/22/2013] [Accepted: 05/15/2013] [Indexed: 11/21/2022]
Abstract
Amelogenin, the major extracellular enamel matrix protein, plays a critical role in regulating the growth and organization of enamel. Assembly and mineralization of full-length native (P173) and recombinant (rP172) porcine amelogenins were studied by cryogenic Transmission Electron Microscopy (cryoTEM). The cryoTEM revealed that both native and recombinant porcine amelogenins undergo step-wise self-assembly. Although the overall structural organization of P173 and rP172 oligomers was similar and resembled oligomers of murine recombinant amelogenin rM179, there were subtle differences suggesting that a single phosphorylated serine present in P173 might affect amelogenin self-assembly. Our mineralization studies demonstrated that both P173 and rP172 oligomers stabilize initial mineral clusters. Importantly, however, rP172 regulated the organization of initial mineral clusters into linear chains and guided the formation of parallel arrays of elongated mineral particles, which are the hallmark of enamel structural organization. These results are similar to those obtained previously using full-length recombinant murine amelogenin (Fang et al., 2011a). In contrast to that seen with rP172, phosphorylated P173 strongly inhibits mineralization for extended periods of time. We propose that these differences might be due to the differences in the structural organization and charge distribution between P173 and rP172. Overall our studies indicate that self-assembly of amelogenin and the mechanisms of its control over mineralization might be universal across different mammalian species. Our data also provide new insight into the effect of phosphorylation on amelogenin self-assembly and its regulation of mineralization.
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23
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Bromley KM, Lakshminarayanan R, Thompson M, Lokappa SB, Gallon VA, Cho KR, Qiu SR, Moradian-Oldak J. Amelogenin processing by MMP-20 prevents protein occlusion inside calcite crystals. CRYSTAL GROWTH & DESIGN 2012; 12:4897-4905. [PMID: 23226976 PMCID: PMC3513936 DOI: 10.1021/cg300754a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Calcite crystals were grown in the presence of full-length amelogenin and during its proteolysis by recombinant human matrix metalloproteinase 20 (rhMMP-20). Recombinant porcine amelogenin (rP172) altered the shape of calcite crystals by inhibiting the growth of steps on the {104} faces and became occluded inside the crystals. Upon co-addition of rhMMP-20, the majority of the protein was digested resulting in a truncated amelogenin lacking the C-terminal segment. In rP172-rhMMP-20 samples, the occlusion of amelogenin into the calcite crystals was drastically decreased. Truncated amelogenin (rP147) and the 25-residue C-terminal domain produced crystals with regular shape and less occluded organic material. Removal of the C-terminal diminished the affinity of amelogenin to the crystals and therefore prevented occlusion. We hypothesize that HAP and calcite interact with amelogenin in a similar manner. In the case of each material, full-length amelogenin binds most strongly, truncated amelogenin binds weakly and the C-terminus alone has the weakest interaction. Regarding enamel crystal growth, the prevention of occlusion into maturing enamel crystals might be a major benefit resulting from the selective cleavage of amelogenin at the C-terminus by MMP-20. Our data have important implications for understanding the hypomineralized enamel phenotype in cases of amelogenesis imperfecta resulting from MMP-20 mutations and will contribute to the design of enamel inspired biomaterials.
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Affiliation(s)
- Keith M. Bromley
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Rajamani Lakshminarayanan
- Centre for Translational Medicine, NUS, Yong Loo Lin School of Medicine, 14 Medical Drive, Singapore Eye Research Institute (SERI), Level 8-South Core, Singapore 117599
| | - Mitchell Thompson
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Sowmya B. Lokappa
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Victoria A. Gallon
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
| | - Kang R. Cho
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
- Lawrence Berkeley National Laboratory, One Cyclotron Rd., MS 67R1235A, Berkeley, CA 94720, USA
| | - S. Roger Qiu
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
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Le Norcy E, Kwak SY, Allaire M, Fratzl P, Yamakoshi Y, Simmer JP, Margolis HC. Effect of phosphorylation on the interaction of calcium with leucine-rich amelogenin peptide. Eur J Oral Sci 2012; 119 Suppl 1:97-102. [PMID: 22243234 DOI: 10.1111/j.1600-0722.2011.00900.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Amelogenin undergoes self-assembly and plays an essential role in guiding enamel mineral formation. The leucine-rich amelogenin peptide (LRAP) is an alternative splice product of the amelogenin gene and is composed of the N terminus (containing the only phosphate group) and the C terminus of full-length amelogenin. This study was conducted to investigate further the role of phosphorylation in LRAP self-assembly in the presence and absence of calcium using small angle X-ray scattering (SAXS). Consistent with our previous dynamic light-scattering findings for phosphorylated (+P) and non-phosphorylated (-P) LRAP, SAXS analyses revealed radii of gyration (R(g)) for LRAP(-P) (46.3-48.0 Å) that were larger than those for LRAP(+P) (25.0-27.4 Å) at pH 7.4. However, added calcium (up to 2.5 mM) induced significant increases in the R(g) of LRAP(+P) (up to 46.4 Å), while it had relatively little effect on LRAP(-P) particle size. Furthermore, SAXS analyses suggested compact folded structures for LRAP(-P) in the presence and absence of calcium, whereas the conformation of LRAP(+P) changed from an unfolded structure to a more compact structure upon the addition of calcium. We conclude that the single phosphate group in LRAP(+P) induces functionally important conformational changes, suggesting that phosphorylation may also influence amelogenin conformation and protein-mineral interactions during the early stages of amelogenesis.
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Affiliation(s)
- Elvire Le Norcy
- Department of Biomineralization, The Forsyth Institute, Cambridge, MA 02142, USA
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25
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Gungormus M, Oren EE, Horst JA, Fong H, Hnilova M, Somerman MJ, Snead ML, Samudrala R, Tamerler C, Sarikaya M. Cementomimetics-constructing a cementum-like biomineralized microlayer via amelogenin-derived peptides. Int J Oral Sci 2012; 4:69-77. [PMID: 22743342 PMCID: PMC3412665 DOI: 10.1038/ijos.2012.40] [Citation(s) in RCA: 40] [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: 03/12/2012] [Accepted: 05/03/2012] [Indexed: 01/09/2023] Open
Abstract
Cementum is the outer-, mineralized-tissue covering the tooth root and an essential part of the system of periodontal tissue that anchors the tooth to the bone. Periodontal disease results from the destructive behavior of the host elicited by an infectious biofilm adhering to the tooth root and left untreated, may lead to tooth loss. We describe a novel protocol for identifying peptide sequences from native proteins with the potential to repair damaged dental tissues by controlling hydroxyapatite biomineralization. Using amelogenin as a case study and a bioinformatics scoring matrix, we identified regions within amelogenin that are shared with a set of hydroxyapatite-binding peptides (HABPs) previously selected by phage display. One 22-amino acid long peptide regions referred to as amelogenin-derived peptide 5 (ADP5) was shown to facilitate cell-free formation of a cementum-like hydroxyapatite mineral layer on demineralized human root dentin that, in turn, supported attachment of periodontal ligament cells in vitro. Our findings have several implications in peptide-assisted mineral formation that mimic biomineralization. By further elaborating the mechanism for protein control over the biomineral formed, we afford new insights into the evolution of protein-mineral interactions. By exploiting small peptide domains of native proteins, our understanding of structure-function relationships of biomineralizing proteins can be extended and these peptides can be utilized to engineer mineral formation. Finally, the cementomimetic layer formed by ADP5 has the potential clinical application to repair diseased root surfaces so as to promote the regeneration of periodontal tissues and thereby reduce the morbidity associated with tooth loss.
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Affiliation(s)
- Mustafa Gungormus
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
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26
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Abstract
Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principels of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties and the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth.
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Affiliation(s)
- Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA.
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Feng J, McDaniel JS, Chuang HH, Huang O, Rakian A, Xu X, Steffensen B, Donly KJ, MacDougall M, Chen S. Binding of amelogenin to MMP-9 and their co-expression in developing mouse teeth. J Mol Histol 2012; 43:473-85. [PMID: 22648084 PMCID: PMC3460178 DOI: 10.1007/s10735-012-9423-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/29/2012] [Indexed: 12/02/2022]
Abstract
Amelogenin is the most abundant matrix protein in enamel. Proper amelogenin processing by proteinases is necessary for its biological functions during amelogenesis. Matrix metalloproteinase 9 (MMP-9) is responsible for the turnover of matrix components. The relationship between MMP-9 and amelogenin during tooth development remains unknown. We tested the hypothesis that MMP-9 binds to amelogenin and they are co-expressed in ameloblasts during amelogenesis. We evaluated the distribution of both proteins in the mouse teeth using immunohistochemistry and confocal microscopy. At postnatal day 2, the spatial distribution of amelogenin and MMP-9 was co-localized in preameloblasts, secretory ameloblasts, enamel matrix and odontoblasts. At the late stages of mouse tooth development, expression patterns of amelogenin and MMP-9 were similar to that seen in postnatal day 2. Their co-expression was further confirmed by RT-PCR, Western blot and enzymatic zymography analyses in enamel organ epithelial and odontoblast-like cells. Immunoprecipitation assay revealed that MMP-9 binds to amelogenin. The MMP-9 cleavage sites in amelogenin proteins across species were found using bio-informative software program. Analyses of these data suggest that MMP-9 may be involved in controlling amelogenin processing and enamel formation.
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Affiliation(s)
- Junsheng Feng
- Department of Developmental Dentistry, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
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Lee KE, Lee SK, Jung SE, Song SJ, Cho SH, Lee ZH, Kim JW. A novel mutation in the AMELX gene and multiple crown resorptions. Eur J Oral Sci 2012; 119 Suppl 1:324-8. [DOI: 10.1111/j.1600-0722.2011.00858.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Hierarchical self-assembly of amelogenin and the regulation of biomineralization at the nanoscale. Proc Natl Acad Sci U S A 2011; 108:14097-102. [PMID: 21825148 DOI: 10.1073/pnas.1106228108] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Enamel is a highly organized hierarchical nanocomposite, which consists of parallel arrays of elongated apatitic crystallites forming an intricate three-dimensional microstructure. Amelogenin, the major extracellular matrix protein of dental enamel, regulates the formation of these crystalline arrays via cooperative interactions with forming mineral phase. Using cryoelectron microscopy, we demonstrate that amelogenin undergoes stepwise hierarchical self-assembly. Furthermore, our results indicate that interactions between amelogenin hydrophilic C-terminal telopeptides are essential for oligomer formation and for subsequent steps of hierarchical self-assembly. We further show that amelogenin assemblies stabilize mineral prenucleation clusters and guide their arrangement into linear chains that organize as parallel arrays. The prenucleation clusters subsequently fuse together to form needle-shaped mineral particles, leading to the formation of bundles of crystallites, the hallmark structural organization of the forming enamel at the nanoscale. These findings provide unique insight into the regulation of biological mineralization by specialized macromolecules and an inspiration for bottom-up strategies for the materials design.
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Le Norcy E, Kwak SY, Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Leucine-rich amelogenin peptides regulate mineralization in vitro. J Dent Res 2011; 90:1091-7. [PMID: 21653221 DOI: 10.1177/0022034511411301] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Amelogenin's capacity to regulate enamel formation is related to its conserved N- and C-terminal domains, its ability to self-assemble, and its ability to stabilize amorphous calcium phosphate (ACP) - a capacity enhanced by amelogenin phosphorylation. This in vitro study provides further insight into amelogenin function, using variations of the Leucine-Rich Amelogenin Peptide (LRAP), an alternative splice product comprised solely of amelogenin's N- and C-terminal domains. Peptide self-assembly was studied by dynamic light-scattering and transmission electron microscopy (TEM). TEM, selected area electron diffraction, and Fourier transform-infrared spectroscopy were also used to determine the effect of phosphorylated and non-phosphorylated LRAP on calcium phosphate formation. Results show that phosphorylated and non-phosphorylated LRAP can self-assemble into chain-like structures in a fashion dependent on the C-terminal domain. Notably, this capacity was enhanced by added calcium and to a much greater degree for phosphorylated LRAP. Furthermore, phosphorylated LRAP was found to stabilize ACP and prevent its transformation to hydroxyapatite (HA), while aligned HA crystals formed in the presence of non-phosphorylated LRAP. The N- and C-terminal amelogenin domains in non-phosphorylated LRAP are, therefore, sufficient to guide ACP transformation into ordered bundles of apatite crystals, making LRAP an excellent candidate for biomimetic approaches for enamel regeneration.
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Affiliation(s)
- E Le Norcy
- Department of Biomineralization, The Forsyth Institute, 245 First Street, Cambridge, MA 02142, USA
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Fang PA, Margolis HC, Conway JF, Simmer JP, Dickinson GH, Beniash E. Cryogenic transmission electron microscopy study of amelogenin self-assembly at different pH. Cells Tissues Organs 2011; 194:166-70. [PMID: 21597263 DOI: 10.1159/000324250] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cryogenic transmission electron microscopy (cryo-EM) was used to explore the self-assembly of recombinant murine amelogenin (rM179) in vitro. Our cryo-EM data showed that amelogenin self-assembly is a strongly pH-dependent process. At pH 4.4 the main fraction of the protein exists in a monomeric form, although some peculiar structures consisting of chains of monomers were also observed. At pH 5.8 large nanospheres comprising ring-like structures ~50 nm in diameter were the most abundant particle class. Similarly, at pH 8.0 amelogenins self-assembled into ring-like oligomers of different sizes, which subsequently assembled into nanospheres 15-20 nm in diameter. Furthermore, at pH 7.2, which is close to a physiological pH, branched chains of nanospheres were observed. Our results show that amelogenin assembly is a multistep hierarchical process and provides new insight into the control of enamel mineralization.
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Affiliation(s)
- Ping-An Fang
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA
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Le Norcy E, Kwak SY, Wiedemann-Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Potential role of the amelogenin N-terminus in the regulation of calcium phosphate formation in vitro. Cells Tissues Organs 2011; 194:188-93. [PMID: 21576914 DOI: 10.1159/000324827] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
N-terminal and C-terminal (CT) domains of amelogenin have been shown to be essential for proper enamel formation. Recent studies have also suggested that although the C-terminus plays an apparent role in protein-mineral interactions, other amelogenin structural domains are involved. The objective was to explore the role of the amelogenin N-terminus in the regulation of calcium phosphate formation in vitro. Spontaneous mineralization studies were carried out using the phosphorylated (+P) and nonphosphorylated (-P) N-terminus of the leucine-rich amelogenin peptide (LRAP) that lacks the hydrophilic CT domain. Mineralization progress was monitored via changes in solution pH. Mineral phases formed were characterized using TEM, selected area electron diffraction, and FT-IR. In controls, amorphous calcium phosphate was initially formed and subsequently transformed to randomly oriented hydroxyapatite (HA) plate-like crystals. In contrast to the control, LRAP(+P)-CT stabilized ACP formation for >1 day, while LRAP(-P)-CT accelerated the transformation of ACP to HA but had little effect on crystal shape or orientation. In conclusion, the N-terminal domain found in LRAP, as in amelogenins, appears to have the capacity to interact with forming calcium phosphate mineral phases. Results suggest that the N-terminal domain of amelogenin may play a direct role in early stages of enamel formation.
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Affiliation(s)
- E Le Norcy
- Department of Biomineralization, The Forsyth Institute, Cambridge, Mass., USA
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Li Y, Pugach MK, Kuehl MA, Peng L, Bouchard J, Hwang SY, Gibson CW. Dental enamel structure is altered by expression of dominant negative RhoA in ameloblasts. Cells Tissues Organs 2011; 194:227-31. [PMID: 21576911 DOI: 10.1159/000324559] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Using in vitrotooth germ cultures and analysis by confocal microscopy, ameloblasts treated with sodium fluoride were found to have elevated amounts of filamentous actin. Because this response is reduced by inhibitors of the Rho/ROCK signaling pathway, we generated mice that express dominant negative RhoA (RhoA(DN)) in ameloblasts for in vivo analysis. Expression of the EGFP-RhoA(DN) fusion protein was evaluated by RT-PCR and immunohistochemistry, and teeth were analyzed by scanning electron microscopy. The 3 strains expressed at either low (TgEGFP-RhoA(DN)-8), intermediate (TgEGFP-RhoA(DN)-2), or high (TgEGFP-RhoA(DN)-13) levels, and the molar teeth from the 3 strains had enamel hypoplasia and surface defects. We conclude that RhoA(DN) expressed in ameloblasts interferes with normal enamel development through the pathway that is induced by sodium fluoride.
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Affiliation(s)
- Yong Li
- Department of Anatomy and Cell Biology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pa., USA
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