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Mechanics of amelogenin TRAP protein in the proximity of hydroxyapatite mineral is altered by interfacial water. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.02.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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2
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Lacruz RS, Habelitz S, Wright JT, Paine ML. DENTAL ENAMEL FORMATION AND IMPLICATIONS FOR ORAL HEALTH AND DISEASE. Physiol Rev 2017; 97:939-993. [PMID: 28468833 DOI: 10.1152/physrev.00030.2016] [Citation(s) in RCA: 223] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/10/2017] [Accepted: 01/10/2017] [Indexed: 12/16/2022] Open
Abstract
Dental enamel is the hardest and most mineralized tissue in extinct and extant vertebrate species and provides maximum durability that allows teeth to function as weapons and/or tools as well as for food processing. Enamel development and mineralization is an intricate process tightly regulated by cells of the enamel organ called ameloblasts. These heavily polarized cells form a monolayer around the developing enamel tissue and move as a single forming front in specified directions as they lay down a proteinaceous matrix that serves as a template for crystal growth. Ameloblasts maintain intercellular connections creating a semi-permeable barrier that at one end (basal/proximal) receives nutrients and ions from blood vessels, and at the opposite end (secretory/apical/distal) forms extracellular crystals within specified pH conditions. In this unique environment, ameloblasts orchestrate crystal growth via multiple cellular activities including modulating the transport of minerals and ions, pH regulation, proteolysis, and endocytosis. In many vertebrates, the bulk of the enamel tissue volume is first formed and subsequently mineralized by these same cells as they retransform their morphology and function. Cell death by apoptosis and regression are the fates of many ameloblasts following enamel maturation, and what cells remain of the enamel organ are shed during tooth eruption, or are incorporated into the tooth's epithelial attachment to the oral gingiva. In this review, we examine key aspects of dental enamel formation, from its developmental genesis to the ever-increasing wealth of data on the mechanisms mediating ionic transport, as well as the clinical outcomes resulting from abnormal ameloblast function.
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Affiliation(s)
- Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - Stefan Habelitz
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - J Timothy Wright
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - Michael L Paine
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
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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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Full-length amelogenin influences the differentiation of human dental pulp stem cells. Stem Cell Res Ther 2016; 7:10. [PMID: 26762641 PMCID: PMC4712507 DOI: 10.1186/s13287-015-0269-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 11/30/2015] [Accepted: 12/21/2015] [Indexed: 12/25/2022] Open
Abstract
Background Amelogenin is an extracellular matrix protein well known for its role in the organization and mineralization of enamel. Clinically, it is used for periodontal regeneration and, due to its finding also in predentin and intercellular spaces of dental pulp cells, it has recently been suggested for pulp capping procedures. The aim of this study was to analyse in vitro the effect of the recombinant human full-length amelogenin on the growth and differentiation of human dental pulp stem cells (hDPSCs). Methods Human DPSCs were treated with a supplement of amelogenin at a concentration of 10 ng/ml, 100 ng/ml and 1000 ng/ml. The groups were compared to the unstimulated control in terms of cell morphology and proliferation, mineralization and gene expression for ALP (alkaline phosphatase), DMP1 (dentin matrix protein-1) and DSPP (dentin sialophosphoprotein). Results Amelogenin affects hDPSCs differently than PDL (periodontal ligament) cells and other cell lines. The proliferation rate at two weeks is significantly reduced in presence of the highest concentration of amelogenin as compared to the unstimulated control. hDPSCs treated with low concentrations present a downregulation of DMP1 and DSPP, which is significant for DSPP (p = 0.011), but not for DMP1 (p = 0.395). Conclusions These finding suggest that the role of full-length amelogenin is not restricted to participation in tooth structure. It influences the differentiation of hDPSC according to various concentrations and this might impair the clinical results of pulp capping.
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Bioactive nanofibers enable the identification of thrombospondin 2 as a key player in enamel regeneration. Biomaterials 2015; 61:216-28. [PMID: 26004236 DOI: 10.1016/j.biomaterials.2015.05.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 05/14/2015] [Accepted: 05/18/2015] [Indexed: 12/19/2022]
Abstract
Tissue regeneration and development involves highly synchronized signals both between cells and with the extracellular environment. Biomaterials can be tuned to mimic specific biological signals and control cell response(s). As a result, these materials can be used as tools to elucidate cell signaling pathways and candidate molecules involved with cellular processes. In this work, we explore enamel-forming cells, ameloblasts, which have a limited regenerative capacity. By exposing undifferentiated cells to a self-assembling matrix bearing RGDS epitopes, we elicited a regenerative signal at will that subsequently led to the identification of thrombospondin 2 (TSP2), an extracellular matrix protein that has not been previously recognized as a key player in enamel development and regeneration. Targeted disruption of the thrombospondin 2 gene (Thbs2) resulted in enamel formation with a disordered architecture that was highly susceptible to wear compared to their wild-type counterparts. To test the regenerative capacity, we injected the bioactive matrix into the enamel organ and discovered that the enamel organic epithelial cells in TSP-null mice failed to polarize on the surface of the artificial matrix, greatly reducing integrin β1 and Notch1 expression levels, which represent signaling pathways known to be associated with TSP2. These results suggest TSP2 plays an important role in regulating cell-matrix interactions during enamel formation. Exploiting the signaling pathways activated by biomaterials can provide insight into native signaling mechanisms crucial for tooth development and cell-based strategies for enamel regeneration.
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Wald T, Osickova A, Sulc M, Benada O, Semeradtova A, Rezabkova L, Veverka V, Bednarova L, Maly J, Macek P, Sebo P, Slaby I, Vondrasek J, Osicka R. Intrinsically disordered enamel matrix protein ameloblastin forms ribbon-like supramolecular structures via an N-terminal segment encoded by exon 5. J Biol Chem 2013; 288:22333-45. [PMID: 23782691 DOI: 10.1074/jbc.m113.456012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tooth enamel, the hardest tissue in the body, is formed by the evolutionarily highly conserved biomineralization process that is controlled by extracellular matrix proteins. The intrinsically disordered matrix protein ameloblastin (AMBN) is the most abundant nonamelogenin protein of the developing enamel and a key element for correct enamel formation. AMBN was suggested to be a cell adhesion molecule that regulates proliferation and differentiation of ameloblasts. Nevertheless, detailed structural and functional studies on AMBN have been substantially limited by the paucity of the purified nondegraded protein. With this study, we have developed a procedure for production of a highly purified form of recombinant human AMBN in quantities that allowed its structural characterization. Using size exclusion chromatography, analytical ultracentrifugation, transmission electron, and atomic force microscopy techniques, we show that AMBN self-associates into ribbon-like supramolecular structures with average widths and thicknesses of 18 and 0.34 nm, respectively. The AMBN ribbons exhibited lengths ranging from tens to hundreds of nm. Deletion analysis and NMR spectroscopy revealed that an N-terminal segment encoded by exon 5 comprises two short independently structured regions and plays a key role in self-assembly of AMBN.
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Affiliation(s)
- Tomas Wald
- Institute of Microbiology, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic
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Tian K, Peng M, Ren X, Liao C, Fei W. Regeneration of tooth-like hydroxyapatite depended on amelogenin functional section monolayer: A new approach for tooth repair. Med Hypotheses 2012; 79:143-6. [DOI: 10.1016/j.mehy.2012.04.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 04/01/2012] [Indexed: 11/29/2022]
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Holcroft J, Ganss B. Identification of amelotin- and ODAM-interacting enamel matrix proteins using the yeast two-hybrid system. Eur J Oral Sci 2012; 119 Suppl 1:301-6. [PMID: 22243260 DOI: 10.1111/j.1600-0722.2011.00870.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The formation of dental enamel is a prototype of functional tissue development through biomineralization. Amelotin (AMTN) is a recently discovered secreted enamel protein predominantly expressed during the maturation stage of enamel formation. It accumulates in a basal lamina-like structure at the interface between ameloblasts and enamel mineral and it co-localizes with another recently described enamel protein, odontogenic ameloblast-associated protein (ODAM). The purpose of this study was to determine whether AMTN and ODAM bind to each other and/or to other well-established enamel matrix proteins. The coding sequences of all enamel proteins were cloned into appropriate vectors of the GAL4-based Matchmaker Gold Yeast Two-Hybrid System. The growth of yeast cells on selective media and color induction were used as indicators for reporter gene expression through protein-protein interactions in combinations of prey and bait constructs. We found that AMTN interacts with itself and with ODAM, but not with amelogenin (AMEL), ameloblastin (AMBN), or enamelin (ENAM). Using ODAM as bait, the interaction with AMTN was confirmed. Furthermore, ODAM was found to bind to itself and to AMBN, as well as weakly to AMEL but not to ENAM. We propose a model where the distinct expression of AMTN and ODAM and their interaction are involved in defining the enamel microstructure at the enamel surface.
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Affiliation(s)
- James Holcroft
- Matrix Dynamics Group, University of Toronto, Faculty of Dentistry, Toronto, ON, Canada
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Cheng ZJ, Wang Q, Wang XM, Cui FZ, Ge J, Chen D, Tian LL. Enamel distribution, structure and mechanical alterations in col1-caPPR mice molar. Arch Oral Biol 2011; 56:1020-6. [DOI: 10.1016/j.archoralbio.2011.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 03/21/2011] [Accepted: 03/22/2011] [Indexed: 10/18/2022]
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Lacruz RS, Lakshminarayanan R, Bromley KM, Hacia JG, Bromage TG, Snead ML, Moradian-Oldak J, Paine ML. Structural analysis of a repetitive protein sequence motif in strepsirrhine primate amelogenin. PLoS One 2011; 6:e18028. [PMID: 21437261 PMCID: PMC3060920 DOI: 10.1371/journal.pone.0018028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 02/18/2011] [Indexed: 11/29/2022] Open
Abstract
Strepsirrhines are members of a primate suborder that has a distinctive set of features associated with the development of the dentition. Amelogenin (AMEL), the better known of the enamel matrix proteins, forms 90% of the secreted organic matrix during amelogenesis. Although AMEL has been sequenced in numerous mammalian lineages, the only reported strepsirrhine AMEL sequences are those of the ring-tailed lemur and galago, which contain a set of additional proline-rich tandem repeats absent in all other primates species analyzed to date, but present in some non-primate mammals. Here, we first determined that these repeats are present in AMEL from three additional lemur species and thus are likely to be widespread throughout this group. To evaluate the functional relevance of these repeats in strepsirrhines, we engineered a mutated murine amelogenin sequence containing a similar proline-rich sequence to that of Lemur catta. In the monomeric form, the MQP insertions had no influence on the secondary structure or refolding properties, whereas in the assembled form, the insertions increased the hydrodynamic radii. We speculate that increased AMEL nanosphere size may influence enamel formation in strepsirrhine primates.
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Affiliation(s)
- Rodrigo S. Lacruz
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, United States of America
| | | | - Keith M. Bromley
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, United States of America
| | - Joseph G. Hacia
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California, United States of America
| | - Timothy G. Bromage
- Departments of Biomaterials and Biomimetics and Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York, United States of America
| | - Malcolm L. Snead
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, United States of America
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, United States of America
| | - Michael L. Paine
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, United States of America
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11
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Snead ML, Zhu DH, Lei Y, Luo W, Bringas PO, Sucov HM, Rauth RJ, Paine ML, White SN. A simplified genetic design for mammalian enamel. Biomaterials 2011; 32:3151-7. [PMID: 21295848 DOI: 10.1016/j.biomaterials.2011.01.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 01/08/2011] [Indexed: 01/30/2023]
Abstract
A biomimetic replacement for tooth enamel is urgently needed because dental caries is the most prevalent infectious disease to affect man. Here, design specifications for an enamel replacement material inspired by Nature are deployed for testing in an animal model. Using genetic engineering we created a simplified enamel protein matrix precursor where only one, rather than dozens of amelogenin isoforms, contributed to enamel formation. Enamel function and architecture were unaltered, but the balance between the competing materials properties of hardness and toughness was modulated. While the other amelogenin isoforms make a modest contribution to optimal biomechanical design, the enamel made with only one amelogenin isoform served as a functional substitute. Where enamel has been lost to caries or trauma a suitable biomimetic replacement material could be fabricated using only one amelogenin isoform, thereby simplifying the protein matrix parameters by one order of magnitude.
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Affiliation(s)
- Malcolm L Snead
- Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA.
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12
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Notman R, Oren EE, Tamerler C, Sarikaya M, Samudrala R, Walsh TR. Solution Study of Engineered Quartz Binding Peptides Using Replica Exchange Molecular Dynamics. Biomacromolecules 2010; 11:3266-74. [DOI: 10.1021/bm100646z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rebecca Notman
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
| | - E. Emre Oren
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
| | - Candan Tamerler
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
| | - Mehmet Sarikaya
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
| | - Ram Samudrala
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
| | - Tiffany R. Walsh
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, United Kingdom, Genetically Engineered Materials Science and Engineering Center, and Departments of Materials Science and Engineering and Microbiology, University of Washington, Seattle, Washington, United States
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Palmer LC, Newcomb CJ, Kaltz SR, Spoerke ED, Stupp SI. Biomimetic systems for hydroxyapatite mineralization inspired by bone and enamel. Chem Rev 2008; 108:4754-83. [PMID: 19006400 PMCID: PMC2593885 DOI: 10.1021/cr8004422] [Citation(s) in RCA: 647] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Liam C Palmer
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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14
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Zou Y, Wang H, Shapiro J, Okamoto C, Brookes S, Lyngstadaas S, Snead M, Paine M. Determination of protein regions responsible for interactions of amelogenin with CD63 and LAMP1. Biochem J 2007; 408:347-54. [PMID: 17708745 PMCID: PMC2267358 DOI: 10.1042/bj20070881] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Revised: 08/10/2007] [Accepted: 08/21/2007] [Indexed: 01/13/2023]
Abstract
The enamel matrix protein amelogenin is secreted by ameloblasts into the extracellular space to guide the formation of highly ordered hydroxyapatite mineral crystallites, and, subsequently, is almost completely removed during mineral maturation. Amelogenin interacts with the transmembrane proteins CD63 and LAMP (lysosome-associated membrane protein) 1, which are involved in endocytosis. Exogenously added amelogenin has been observed to move rapidly into CD63/LAMP1-positive vesicles in cultured cells. In the present study, we demonstrate the protein region defined by amino acid residues 103-205 for CD63 interacts not only with amelogenin, but also with other enamel matrix proteins (ameloblastin and enamelin). A detailed characterization of binding regions in amelogenin, CD63 and LAMP1 reveals that the amelogenin region defined by residues PLSPILPELPLEAW is responsible for the interaction with CD63 through residues 165-205, with LAMP1 through residues 226-251, and with the related LAMP2 protein through residues 227-259. We predict that the amelogenin binding region is: (i) hydrophobic; (ii) largely disordered; and (iii) accessible to the external environment. In contrast, the binding region of CD63 is likely to be organized in a '7' shape within the mushroom-like structure of CD63 EC2 (extracellular domain 2). In vivo, the protein interactions between the secreted enamel matrix proteins with the membrane-bound proteins are likely to occur at the specialized secretory surfaces of ameloblast cells called Tomes' processes. Such protein-protein interactions may be required to establish short-term order of the forming matrix and/or to mediate feedback signals to the transcriptional machinery of ameloblasts and/or to remove matrix protein debris during enamel biomineralization.
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Affiliation(s)
- YanMing Zou
- *University of Southern California School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 103, Los Angeles, CA 90033-1004, U.S.A
| | - HongJun Wang
- *University of Southern California School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 103, Los Angeles, CA 90033-1004, U.S.A
| | - Jason L. Shapiro
- *University of Southern California School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 103, Los Angeles, CA 90033-1004, U.S.A
| | - Curtis T. Okamoto
- †University of Southern California School of Pharmacy, Department of Pharmacology and Pharmaceutical Sciences, Los Angeles, CA 90089-9121, U.S.A
| | - Steven J. Brookes
- ‡Department of Oral Biology, Leeds Dental Institute, University of Leeds, Clarendon Way, Leeds LS2 9LU, U.K
| | - S. Petter Lyngstadaas
- §Department of Biomaterials, Faculty of Dentistry, University of Oslo, P.O. Box 1109 Blindern, N-0317 Oslo, Norway
| | - Malcolm L. Snead
- *University of Southern California School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 103, Los Angeles, CA 90033-1004, U.S.A
| | - Michael L. Paine
- *University of Southern California School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 103, Los Angeles, CA 90033-1004, U.S.A
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Shintani S, Kobata M, Toyosawa S, Ooshima T. Expression of ameloblastin during enamel formation in a crocodile. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 306:126-33. [PMID: 16217799 DOI: 10.1002/jez.b.21077] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ameloblastin is an enamel-specific protein that plays critical roles in enamel formation, as well as adhesion between ameloblasts and the enamel matrix, as shown by analyses of ameloblastin-null mice. In the present study, we produced two distinct antibodies that recognize the N-terminus and C-terminus regions of caiman ameloblastin, in order to elucidate the fate of ameloblastin peptides during tooth development. An immunohistochemical study using the antibodies showed that caiman ameloblastin was a tooth-specific matrix protein that may initially be cleaved into two groups, N- and C-terminal peptides, as shown in mammals. The distribution of the N-terminal peptides was much different from that of the C-terminal peptides during enamel formation; however, it was similar to that of mammalian ameloblastin. Although ameloblastin is thought to have a relationship with the enamel prismatic structure in mammals, in the caiman, which has non-prismatic enamel, functional ameloblastin has no relationship with any enamel structure. Consequently, it is suggested that ameloblastin has kept its original functions during the evolutionary transition from reptiles to mammals and that it has been conserved in both lineages during more than 200 million years of evolution. Our results support the notion that ameloblastin acts as a factor for ameloblast adhesion to enamel matrix, because distribution of the C-terminal peptides was consistently restricted on the surface layers of enamel matrix specimens ranging from immature to nearly completely mature. The principal molecules that provide the adhesive function are presumably C-terminal peptides.
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Affiliation(s)
- Seikou Shintani
- Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
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16
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Snead ML, Zhu D, Lei Y, White SN, Snead CM, Luo W, Paine ML. Protein self-assembly creates a nanoscale device for biomineralization. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2006. [DOI: 10.1016/j.msec.2005.08.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Wang HJ, Tannukit S, Wen X, Shapiro JL, Snead ML, Paine ML. Using the yeast two-hybrid assay to discover protein partners for the leucine-rich amelogenin peptide and for tuftelin-interacting protein 11. Eur J Oral Sci 2006; 114 Suppl 1:276-9; discussion 285-6, 382. [PMID: 16674698 DOI: 10.1111/j.1600-0722.2006.00289.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The established structural proteins of the enamel matrix are amelogenin, ameloblastin, and enamelin. Historically, tuftelin and tuftelin-interacting protein 11 (TFIP11) have also been discussed as possible enamel proteins. Protein complexes are achieved by protein-protein interactions, and it is protein complexes that control biomineralization. The purpose of our recent studies was to catalog protein partners for these proteins that are, or have been, implicated in tooth formation. We used the sensitive yeast two-hybrid assay to identify proteins that interact directly with amelogenin, ameloblastin, enamelin, the leucine-rich amelogenin peptide (LRAP) and TFIP11. In this manuscript we refer to, or document, potential protein partners for the proteins listed above. The yeast two-hybrid assay may ultimately prove to be a valuable proteomics methodology for using to decipher molecular events that ultimately result in enamel biomineralization.
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Affiliation(s)
- Hong-Jun Wang
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, CA 90033, USA
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Gibson CW, Kulkarni AB, Wright JT. The use of animal models to explore amelogenin variants in amelogenesis imperfecta. Cells Tissues Organs 2006; 181:196-201. [PMID: 16612085 DOI: 10.1159/000091381] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Amelogenin proteins are secreted by ameloblast cells during tooth development. Because of extensive alternative splicing of the amelogenin primary RNA transcript, and because systematic proteolysis results in many additional peptides during enamel maturation, it has been difficult to assign function to individual amelogenins. Targeted deletions and transgenic mice have been generated in order to better understand amelogenin protein function in vivo. From these murine models, we have determined that amelogenins are responsible for normal enamel thickness and structure, but not for initiation of enamel mineral formation at the dentin-enamel junction. Although it is now clear that the amelogenin (AmelX) gene exists in a nested orientation and that AmelX is expressed at a low level in various developing tissues, the significance of these findings is incompletely understood. Future studies are expected to answer remaining questions concerning structure/function relationships among these 'enamel proteins'.
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Affiliation(s)
- Carolyn W Gibson
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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19
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Brookes SJ, Lyngstadaas SP, Robinson C, Shore RC, Kirkham J. Intracellular nanosphere subunit assembly as revealed by amelogenin molecular cross-linking studies. Eur J Oral Sci 2006; 114 Suppl 1:280-4; discussion 285-6, 382. [PMID: 16674699 DOI: 10.1111/j.1600-0722.2006.00311.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enamel matrix comprises nanospheres predominantly composed of amelogenin. Studies have shown that recombinant amelogenin forms nanospheres similar to those formed in vivo, but it is unclear exactly how nanospheres assemble in vivo. Are amelogenin monomers secreted into the enamel matrix where they then self-assemble to form nanospheres, or does nanosphere assembly actually occur intracellularly? The aim of this study was to attempt to answer this question. Rat enamel organs were treated with the bifunctional cross-linker, dithio bis (succinimidyl propionate) (DSP), which cross-links primary amines lying in close molecular proximity. The key to this technique is the fact that DSP cross-links are later sensitive to reductive cleavage. The cross-linked proteins were first subjected to non-reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) in the first dimension and then to reducing SDS-PAGE in the second dimension (so-called diagonal electrophoresis) followed by western blot probing with anti-amelogenin. The results indicated that intracellular amelogenin monomers are in close neighbor contact, forming complexes comprising up to six individual amelogenin monomers. We suggest that these initial complexes are prefabricated intracellularly before secretion. Once secreted, these prefabricated subunits assemble further to form the mature full-size nanospheres containing hundreds of individual amelogenins characteristic of enamel matrix.
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Affiliation(s)
- Steven J Brookes
- Department of Oral Biology, Leeds Dental Institute, Leeds, UK, and Oral Research Laboratory, Faculty of Dentistry, University of Oslo, Norway.
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20
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Bartlett JD, Ganss B, Goldberg M, Moradian-Oldak J, Paine ML, Snead ML, Wen X, White SN, Zhou YL. Protein–Protein Interactions of the Developing Enamel Matrix. Curr Top Dev Biol 2006; 74:57-115. [PMID: 16860665 DOI: 10.1016/s0070-2153(06)74003-0] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Extracellular matrix proteins control the formation of the inorganic component of hard tissues including bone, dentin, and enamel. The structural proteins expressed primarily in the enamel matrix are amelogenin, ameloblastin, enamelin, and amelotin. Other proteins, like biglycan, are also present in the enamel matrix as well as in other mineralizing and nonmineralizing tissues of mammals. In addition, the presence of sulfated enamel proteins, and "tuft" proteins has been examined and discussed in relation to enamel formation. The structural proteins of the enamel matrix must have specific protein-protein interactions to produce a matrix capable of directing the highly ordered structure of the enamel crystallites. Protein-protein interactions are also likely to occur between the secreted enamel proteins and the plasma membrane of the enamel producing cells, the ameloblasts. Such protein-protein interactions are hypothesized to influence the secretion of enamel proteins, establish short-term order of the forming matrix, and to mediate feedback signals to the transcriptional machinery of these cells. Membrane-bound proteins identified in ameloblasts, and which interact with the structural enamel proteins, include Cd63 (cluster of differentiation 63 antigen), annexin A2 (Anxa2), and lysosomal-associated glycoprotein 1 (Lamp1). These and related data help explain the molecular and cellular mechanisms responsible for the removal of the organic enamel matrix during the events of enamel mineralization, and how the enamel matrix influences its own fate through signaling initiated at the cell surface. The knowledge gained from enamel developmental studies may lead to better dental and nondental materials, or materials inspired by Nature. These data will be critical to scientists, engineers, and dentists in their pursuits to regenerate an entire tooth. For tooth regeneration to become a reality, the protein-protein interactions involving the key dental proteins must be identified and understood. The scope of this review is to discuss the current understanding of protein-protein interactions of the developing enamel matrix, and relate this knowledge to enamel biomineralization.
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Affiliation(s)
- John D Bartlett
- The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
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21
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Paine ML, Snead ML. Tooth developmental biology: disruptions to enamel-matrix assembly and its impact on biomineralization. Orthod Craniofac Res 2005; 8:239-51. [PMID: 16238604 DOI: 10.1111/j.1601-6343.2005.00346.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dental enamel is a composite bioceramic material that is the hardest tissue in the vertebrate body, containing long, thin crystallites of substituted hydroxyapatite (HAP). Over a lifetime of an organism, enamel functions under repeated and immense loads, generally without catastrophic failure. Enamel is a product of ectoderm-derived cells called ameloblasts. Recent investigations on the formation of enamel using cell and molecular approaches are now being coupled to biomechanical investigations at the nanoscale and mesoscale levels. For amelogenin, the principal structural protein for forming enamel, we have identified two domains that are required for its proper self-assembly into supramolecular structures referred to as nanospheres. Nanospheres are believed to control HAP crystal habit. Other structural proteins of the enamel matrix include ameloblastin and enamelin, but little is known about their biological importance. Transgenic animals have been prepared to investigate the effect of overexpression of wild-type or mutated enamel proteins on the developing enamel matrix. Amelogenin transgenes were engineered to contain deletions to either of the two self-assembly domains and these alterations produced significant defects in the enamel. Additional transgenic animal lines have been prepared and studied and each gives additional insights into the mechanisms for enamel biofabrication. This study summarizes the observed enamel phenotypes of recently derived transgenic animals. These data are being used to help define the role of each of the enamel structural proteins in enamel and study how each of these proteins impact on enamel biomineralization.
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Affiliation(s)
- M L Paine
- School of Dentistry, University of Southern California, Los Angeles, 90033, USA.
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22
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Wang H, Tannukit S, Zhu D, Snead ML, Paine ML. Enamel matrix protein interactions. J Bone Miner Res 2005; 20:1032-40. [PMID: 15883644 DOI: 10.1359/jbmr.050111] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 12/15/2004] [Accepted: 01/21/2005] [Indexed: 11/18/2022]
Abstract
UNLABELLED The recognized structural proteins of the enamel matrix are amelogenin, ameloblastin, and enamelin. While a large volume of data exists showing that amelogenin self-assembles into multimeric units referred to as nanospheres, other reports of enamel matrix protein-protein interactions are scant. We believe that each of these enamel matrix proteins must interact with other organic components of ameloblasts and the enamel matrix. Likely protein partners would include integral membrane proteins and additional secreted proteins. INTRODUCTION The purpose of this study was to identify and catalog additional proteins that play a significant role in enamel formation. MATERIALS AND METHODS We used the yeast two-hybrid assay to identify protein partners for amelogenin, ameloblastin, and enamelin. Once identified, RT-PCR was used to assess gene transcription of these newly identified and potential "enamel" proteins in ameloblast-like LS8 cells. RESULTS In the context of this yeast assay, we identified a number of secreted proteins and integral membrane proteins that interact with amelogenin, ameloblastin, and enamelin. Additionally, proteins whose functions range from the inhibition of soft tissue mineralization, calcium ion transport, and phosphorylation events have been identified as protein partners to these enamel matrix proteins. For each protein identified using this screening strategy, future studies are planned to confirm this physiological relationship to biomineralization in vivo. CONCLUSION Identifying integral membrane proteins of the secretory surface of ameloblast cells (Tomes' processes) and additional enamel matrix proteins, based on their abilities to interact with the most abundant enamel matrix proteins, will better define the molecular mechanisms of enamel formation at its most rudimentary level.
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Affiliation(s)
- HongJun Wang
- Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033, USA
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23
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Ravindranath HH, Chen LS, Zeichner-David M, Ishima R, Ravindranath RMH. Interaction between the enamel matrix proteins amelogenin and ameloblastin. Biochem Biophys Res Commun 2004; 323:1075-83. [PMID: 15381109 DOI: 10.1016/j.bbrc.2004.08.207] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Indexed: 10/26/2022]
Abstract
Enamel matrix consists of amelogenin and non-amelogenins. Though amelogenin is not involved in nucleation of minerals, the enamel mineralization is impaired when amelogenin or other matrix protein (ameloblastin/enamelin) genes are mutated. We hypothesize that amelogenin may promote enamel mineralization by interacting with the calcium-binding matrix proteins. Specific binding of amelogenin to N-acetylglucosamine (GlcNAc), GlcNAc-mimicking peptides (GMps), and their carrier proteins and the identification of amelogenin-trityrosyl-motif-peptide (ATMP) as a GlcNAc/GMp-binding domain in amelogenin favor the hypothesis. This study tested the interaction of amelogenin with ameloblastin, a carrier of GMp sequence at intermittent sites. Neither GlcNAc nor sialic acids were identified in the recombinant-ameloblastin. Amelogenin bound to recombinant-ameloblastin in both Western blots and in ELISA. More specifically, [(3)H]ATMP bound to both recombinant and native ameloblastins. Dosimetry and Scatchard analyses showed the specific interaction between ATMP and ameloblastin, suggesting that amelogenin may interact with ameloblastin to form a heteromolecular assembly.
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Affiliation(s)
- Hanumanth H Ravindranath
- Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
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24
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Abstract
The interaction of proteins with solid surfaces is a fundamental phenomenon with implications for nanotechnology, biomaterials and biotechnological processes. Kinetic and thermodynamic studies have long indicated that significant conformational changes may occur as a protein encounters a surface; new techniques are measuring and modeling these changes. Combinatorial and directed evolution techniques have created new peptide sequences that bind specifically to solid surfaces, similar to the natural proteins that regulate crystal growth. Modeling efforts capture kinetics and thermodynamics on the colloidal scale, but detailed treatments of atomic structure are still in development and face the usual challenges of protein modeling. Opportunities abound for fundamental discovery, as well as breakthroughs in biomaterials, biotechnology and nanotechnology.
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Affiliation(s)
- Jeffrey J Gray
- Chemical & Biomolecular Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
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25
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Chen E, Yuan ZA, Wright JT, Hong SP, Li Y, Collier PM, Hall B, D'Angelo M, Decker S, Piddington R, Abrams WR, Kulkarni AB, Gibson CW. The small bovine amelogenin LRAP fails to rescue the amelogenin null phenotype. Calcif Tissue Int 2003; 73:487-95. [PMID: 12958690 DOI: 10.1007/s00223-002-0036-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2002] [Accepted: 03/17/2003] [Indexed: 11/25/2022]
Abstract
Amelogenins are the most abundant secreted proteins in developing dental enamel. These evolutionarily-conserved proteins have important roles in enamel mineral formation, as mutations within the amelogenin gene coding region lead to defects in enamel thickness or mineral structure. Because of extensive alternative splicing of the primary RNA transcript and proteolytic processing of the secreted proteins, it has been difficult to assign functions to individual amelogenins. To address the function of one of the amelogenins, we have created a transgenic mouse that expresses bovine leucine-rich amelogenin peptide (LRAP) in the enamel-secreting ameloblast cells of the dental organ. Our strategy was to breed this transgenic mouse with the recently generated amelogenin knockout mouse, which makes none of the amelogenin proteins and has a severe hypoplastic and disorganized enamel phenotype. It was found that LRAP does not rescue the enamel defect in amelogenin null mice, and enamel remains hypoplastic and disorganized in the presence of this small amelogenin. In addition, LRAP overexpression in the transgenic mouse (wildtype background) leads to pitting in the enamel surface, which may result from excess protein production or altered protein processing due to minor differences between the amino acid compositions of murine and bovine LRAP. Since introduction of bovine LRAP into the amelogenin null mouse does not restore normal enamel structure, it is concluded that other amelogenin proteins are essential for normal appearance and function.
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Affiliation(s)
- E Chen
- Department of Anatomy and Cell Biology, University of Pennsylvania School of Dental Medicine, 240 S. 40th St., Philadelphia, PA, USA
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26
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Viswanathan HL, Berry JE, Foster BL, Gibson CW, Li Y, Kulkarni AB, Snead ML, Somerman MJ. Amelogenin: A Potential Regulator of Cementum-Associated Genes. J Periodontol 2003; 74:1423-31. [PMID: 14653387 DOI: 10.1902/jop.2003.74.10.1423] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Studies suggest that enamel matrix proteins induce differentiation and mineralization of a variety of mesenchymal cells, including odontoblasts, osteoblasts, and cementoblasts. It has been postulated that this activity could be due to amelogenin-like proteins, known to be present in some mixtures of enamel matrix derivatives. Amelogenins have been reported to induce expression of a mineralized tissue-specific marker, bone sialoprotein (BSP), indicating that epithelial products can regulate the activity of mesenchyme-derived cells. METHODS To explore the molecular mechanisms involved in BSP regulation, a clonal population of immortalized murine cementoblasts (OCCM-30) was exposed to full-length murine amelogenin protein (rp(H)M180), 0.1 microg/ml to 10.0 microg/ml, for 8 days in vitro. To further investigate the potential epithelial-mesenchymal interaction, an amelogenin knockout mouse model was used to examine expression of BSP and other markers, including Type I collagen, in tissue samples. RESULTS The lowest dose of amelogenin slightly enhanced BSP expression, whereas at the highest dose, a dramatic decrease (three-fold) in BSP expression was observed. Parallel experiments showed a corresponding decrease in mineral nodule formation in vitro for cells treated with the higher dose of rp(H)M180. In situ hybridization and immunohistochemical analysis of sections from amelogenin null mice revealed a dramatic reduction in expression of BSP mRNA and protein in cementoblasts and surrounding osteoblasts in comparison to age-matched controls. In contrast, the expression of Type I collagen was not significantly different from controls. CONCLUSION These data suggest that amelogenin may be a critical signaling molecule required for appropriate development of the periodontium.
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Affiliation(s)
- Hema L Viswanathan
- Department of Periodontics, Prevention and Geriatrics, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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27
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Paine ML, Wang HJ, Luo W, Krebsbach PH, Snead ML. A transgenic animal model resembling amelogenesis imperfecta related to ameloblastin overexpression. J Biol Chem 2003; 278:19447-52. [PMID: 12657627 DOI: 10.1074/jbc.m300445200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genetic diseases that affect tooth enamel are grouped under the classification amelogenesis imperfecta. Human pedigrees and experiments on transgenic and null mice have all demonstrated that mutations to the secreted proteins amelogenin, enamelin, and enamelysin result in visibly, structurally, or mechanically defective enamel. In an attempt to better define a physiologic function for ameloblastin during enamel formation, we have produced transgenic mice that misexpress the ameloblastin gene. These transgenic animals exhibit imperfections in their enamel that is evident at the nanoscale level. Specifically, ameloblastin overexpression influences enamel crystallite habit and enamel rod morphology. These findings suggest enamel crystallite habit and rod morphology are influenced by the temporal and spatial expression of ameloblastin and may implicate the role of the ameloblastin gene locus in the etiology of a number of undiagnosed autosomally dominant cases of amelogenesis imperfecta.
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Affiliation(s)
- Michael L Paine
- University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, Los Angeles, California 90033, USA.
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28
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Deutsch D, Leiser Y, Shay B, Fermon E, Taylor A, Rosenfeld E, Dafni L, Charuvi K, Cohen Y, Haze A, Fuks A, Mao Z. The human tuftelin gene and the expression of tuftelin in mineralizing and nonmineralizing tissues. Connect Tissue Res 2003; 43:425-34. [PMID: 12489194 DOI: 10.1080/03008200290001186] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Tuftelin has been suggested to play an important role during the development and mineralization of enamel, but its precise function is still unclear. This article reviews major milestones in the discovery, structural characterization, expression, localization, and conservation of tuftelin in different vertebrate species. It focuses on the structure of the human tuftelin gene, which has recently been deciphered [12]. It describes the exon-intron organization, sizes and structure, the promoter structure, and the newly discovered alternatively spliced human tooth-bud tuftelin mRNA transcripts. It also examines information on the structural motifs in the human-derived tuftelin protein and how they relate to tuftelin from other species. It reviews our recent results on the transcription of tuftelin mRNA and protein expression in several nonmineralizing soft tissues, using reverse-transcription polymerase chain reaction (RT-PCR) followed by DNA cloning and sequencing, indirect immunohistochemistry, immunohistochemistry combined with confocal microscopy, and in situ hybridization. These results and earlier Northern blot results show that tuftelin, in addition to being expressed in the developing and mineralizing tooth, is also expressed in several nonmineralizing soft tissues, suggesting that tuftelin has a universal function and/or a multifunctional role.
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Affiliation(s)
- D Deutsch
- Institute of Dental Sciences, Dental Research Unit, Department of Oral Biology, Hebrew University, Hadassah Faculty of Dental Medicine, PO Box 12272, Jerusalem, Israel 91120.
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Paine ML, Lei YP, Dickerson K, Snead ML. Altered amelogenin self-assembly based on mutations observed in human X-linked amelogenesis imperfecta (AIH1). J Biol Chem 2002; 277:17112-6. [PMID: 11877393 DOI: 10.1074/jbc.m110473200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A hallmark of biological systems is a reliance on protein assemblies to perform complex functions. We have focused attention on mammalian enamel formation because it relies on a self-assembling protein complex to direct mineral habit. The principle protein of enamel is amelogenin, a 180-amino acid hydrophobic protein that self-assembles to form nanospheres. We have used independent technical methods, consisting of the yeast two-hybrid (Y2H) assay and surface plasmon resonance (SPR), to demonstrate the importance of amelogenin self-assembly domains. In addition, we have analyzed mutations in amelogenin observed in patients with amelogenesis imperfecta who demonstrate defects in enamel formation. Assessments of self-assembly of these mutant amelogenins by either SPR or Y2H assay yield concordant data. These data support the conclusion that the amelogenin amino-terminal self-assembly domain is essential to the creation of an enamel extracellular organic matrix capable of directing mineral formation. It also suggests that a pathway through which point mutations in the amelogenin protein can adversely impact on the formation of the enamel organ is by disturbing self-assembly of the organic matrix. These data support the utilization of the Y2H assay to search for protein interactions among extracellular matrix proteins that contribute to biomineralization and provide functional information on protein-protein and protein-mineral interactions.
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Affiliation(s)
- Michael L Paine
- University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, Los Angeles, California 90033-1004, USA.
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30
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Mao Z, Shay B, Hekmati M, Fermon E, Taylor A, Dafni L, Heikinheimo K, Lustmann J, Fisher LW, Young MF, Deutsch D. The human tuftelin gene: cloning and characterization. Gene 2001; 279:181-96. [PMID: 11733143 DOI: 10.1016/s0378-1119(01)00749-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Tuftelin has been suggested to play an important role during the development and mineralization of enamel. We isolated the full-length human tuftelin cDNA using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (5' RACE and 3' RACE) methods. Sequence analysis of the tuftelin cDNA revealed an open reading frame of 1170 bp encoding a 390 amino acid protein with a molecular mass of 44.3 kDa and an isoelectric point of 5.7. The human tuftelin protein shares 89 and 88% amino acid sequence identity with the bovine and mouse tuftelin, respectively. It contains a coiled-coil region, recently reported to be involved with tuftelin self-assembly and with the interaction of tuftelin with TIP39 (a novel tuftelin interacting protein). Detailed DNA analysis of the cloned genomic DNA revealed that the human tuftelin gene contains 13 exons and is larger than 26 kb. Two alternatively spliced tuftelin mRNA transcripts have now been identified in the human tooth bud, one lacking exon 2, and the other lacking exon 2 and exon 3. Primer extension analysis, corroborated by RT-PCR and DNA sequencing, revealed multiple transcription initiation sites. The cloned 1.6 kb promoter region contained several GC boxes and several transcription factor binding sites such as those for activator protein 1 and stimulatory protein 1. Our blast search of the human and mouse expressed sequence tag data bases, as well as our RT-PCR and DNA sequencing results, and a previous study using Northern blot analysis revealed that tuftelin cDNA sequences are also expressed in normal and cancerous non-mineralizing soft tissues, suggesting that tuftelin has a universal function. We have now identified and characterized different alternatively spliced mouse tuftelin mRNAs in several non-mineralizing tissues. These results provide an important baseline for future understanding of the biological role of tuftelin.
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Affiliation(s)
- Z Mao
- Dental Research Unit, Department of Oral Biology, Institute of Dental Sciences, Hebrew University, Hadassah Faculty of Dental Medicine, Jerusalem, Israel
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31
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Abstract
Ameloblastin is a tooth-specific extracellular matrix protein that is thought to play a role in enamel crystal formation in the developing dentition. The murine ameloblastin promoter functions in a cell type-specific manner and contains cis-acting elements that function both to enhance and to suppress transcription. The objective of this study was to determine whether the transcription factor Cbfa1, known to be essential for transcription of other mineralized tissue genes, is also required for ameloblastin transcription. Site-directed mutagenesis of the Cbfa1-binding site (-248 base pairs) termed osteoblast-specific element 2 (OSE2) decreased ameloblastin promoter activity by greater than 50% in ameloblast-like cells. No differences in promoter activity were observed in two other oral tissue-derived cell lines transfected with similar constructs. Nuclear factor binding to the ameloblastin promoter was also shown to be cell type-specific and was altered by site-specific mutations in the OSE2 site. Cbfa1 was specifically shown to participate in the DNA-protein complexes between nuclear factors and the ameloblastin OSE2 site by supershift electrophoretic mobility shift assays. The findings that Cbfa1 interacts with functionally important regions of the ameloblastin promoter while promoter activity is diminished in constructs containing site-directed mutations in the Cbfa1 site indicate that Cbfa1 possesses an important function in transcription of the ameloblastin gene.
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Affiliation(s)
- S Dhamija
- University of Michigan School of Dentistry, Department of Oral Medicine, Pathology, and Oncology, Ann Arbor, Michigan 48109-1078, USA
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32
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Paine ML, White SN, Luo W, Fong H, Sarikaya M, Snead ML. Regulated gene expression dictates enamel structure and tooth function. Matrix Biol 2001; 20:273-92. [PMID: 11566262 DOI: 10.1016/s0945-053x(01)00153-6] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Enamel is a complex bioceramic tissue. In its final form, enamel is a reflection of the unique molecular and cellular activities occurring during organogenesis. From the ectodermal origins of ameloblasts, their gene activity and protein expression profiles exist for the sole purpose of producing a mineralized shell, almost entirely devoid of protein, deposited over the 'bone-like' dentine. The interface between enamel and dentine is referred to as the dentine enamel junction and it is also unique in its biology. This review article is narrow in its scope. We restrict our review to selected advances in our understanding of the genetic, molecular and structural aspects of enamel biology. We present a model of enamel formation that relates gene expression to the assembly of an extracellular protein matrix that in turn controls the structural hierarchy and mechanical aspects of enamel and the tooth organ.
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Affiliation(s)
- M L Paine
- University of Southern California, Center for Craniofacial Molecular Biology, Los Angeles, CA 90033, USA.
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White SN, Luo W, Paine ML, Fong H, Sarikaya M, Snead ML. Biological organization of hydroxyapatite crystallites into a fibrous continuum toughens and controls anisotropy in human enamel. J Dent Res 2001; 80:321-6. [PMID: 11269723 DOI: 10.1177/00220345010800010501] [Citation(s) in RCA: 191] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Enamel forms the outer surface of teeth, which are of complex shape and are loaded in a multitude of ways during function. Enamel has previously been assumed to be formed from discrete rods and to be markedly aniostropic, but marked anisotropy might be expected to lead to frequent fracture. Since frequent fracture is not observed, we measured enamel organization using histology, imaging, and fracture mechanics modalities, and compared enamel with crystalline hydroxyapatite (Hap), its major component. Enamel was approximately three times tougher than geologic Hap, demonstrating the critical importance of biological manufacturing. Only modest levels of enamel anisotropy were discerned; rather, our measurements suggest that enamel is a composite ceramic with the crystallites oriented in a complex three-dimensional continuum. Geologic apatite crystals are much harder than enamel, suggesting that inclusion of biological contaminants, such as protein, influences the properties of enamel. Based on our findings, we propose a new structural model.
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Affiliation(s)
- S N White
- Center for Craniofacial Molecular Biology, University of Southern California School of Dentistry, Los Angeles 90033, USA.
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34
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Paine ML, Zhu DH, Luo W, Bringas P, Goldberg M, White SN, Lei YP, Sarikaya M, Fong HK, Snead ML. Enamel biomineralization defects result from alterations to amelogenin self-assembly. J Struct Biol 2000; 132:191-200. [PMID: 11243888 DOI: 10.1006/jsbi.2000.4324] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Enamel formation is a powerful model for the study of biomineralization. A key feature common to all biomineralizing systems is their dependency upon the biosynthesis of an extracellular organic matrix that is competent to direct the formation of the subsequent mineral phase. The major organic component of forming mouse enamel is the 180-amino-acid amelogenin protein (M180), whose ability to undergo self-assembly is believed to contribute to biomineralization of vertebrate enamel. Two recently defined domains (A and B) within amelogenin appear essential for this self-assembly. The significance of these two domains has been demonstrated previously by the yeast two-hybrid system, atomic force microscopy, and dynamic light scattering. Transgenic animals were used to test the hypothesis that the self-assembly domains identified with in vitro model systems also operate in vivo. Transgenic animals bearing either a domain-A-deleted or domain-B-deleted amelogenin transgene expressed the altered amelogenin exclusively in ameloblasts. This altered amelogenin participates in the formation an organic enamel extracellular matrix and, in turn, this matrix is defective in its ability to direct enamel mineralization. At the nanoscale level, the forming matrix adjacent to the secretory face of the ameloblast shows alteration in the size of the amelogenin nanospheres for either transgenic animal line. At the mesoscale level of enamel structural hierarchy, 6-week-old enamel exhibits defects in enamel rod organization due to perturbed organization of the precursor organic matrix. These studies reflect the critical dependency of amelogenin self-assembly in forming a competent enamel organic matrix and that alterations to the matrix are reflected as defects in the structural organization of enamel.
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Affiliation(s)
- M L Paine
- University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, 2250 Alcazar Street, CSA Room 142, Los Angeles, California 90033-1004, USA.
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Paine CT, Paine ML, Luo W, Okamoto CT, Lyngstadaas SP, Snead ML. A tuftelin-interacting protein (TIP39) localizes to the apical secretory pole of mouse ameloblasts. J Biol Chem 2000; 275:22284-92. [PMID: 10806191 DOI: 10.1074/jbc.m000118200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enamel biomineralization is a complex process that involves interactions between extracellular matrix proteins. To identify proteins interacting with tuftelin, a potential nucleator of enamel crystallites, the yeast two-hybrid system was applied to a mouse tooth expression library and a tuftelin-interacting protein (TIP) was isolated for further characterization. Polyclonal antibodies were prepared against two recombinant variants of this protein. Both antibodies identified a major protein product in tooth organs at 39 kDa, and this protein has been called TIP39. Northern analysis showed TIP39 messenger RNA in multiple organs, a pattern similar to that of tuftelin messenger RNA. In situ hybridization of mandibles of 1-day-old mice detected TIP39 RNA in secretory ameloblasts and odontoblasts. Immunolocalization of TIP39 and tuftelin in cultured ameloblast-like cells showed that these two proteins colocalize. Within the developing tooth organ, TIP39 and tuftelin immunolocalized to the apical pole of secretory ameloblasts (Tomes' processes) and to the newly secreted extracellular enamel matrix. TIP39 amino acid sequence appears to be highly conserved with similarities to proteins in species as diverse as yeast and primates. Available sequence data and the findings reported here suggest a role for TIP39 in the secretory pathway of extracellular proteins.
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Affiliation(s)
- C T Paine
- Center for Craniofacial Molecular Biology, University of Southern California School of Dentistry, Los Angeles, California 90033-1004, USA.
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Dhamija S, Liu Y, Yamada Y, Snead ML, Krebsbach PH. Cloning and characterization of the murine ameloblastin promoter. J Biol Chem 1999; 274:20738-43. [PMID: 10400709 DOI: 10.1074/jbc.274.29.20738] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular mechanisms directing the highly restricted expression pattern of murine ameloblastin were characterized by cloning and functional analysis of the ameloblastin promoter. The transcription start site, mapped by primer extension, was located 19 base pairs (bp) 5' of the published cDNA. The promoter was analyzed in a mouse ameloblast-like cell line (LS8) and was compared with promoter activity in primary gingival fibroblasts and pulp fibroblasts. Sequential 5'-deletion mutants encompassing DNA sequences from -1616 to -781 bp exhibited high promoter activity in LS8 cells, whereas the promoter activity decreased to 50% of the full-length construct in the -781- and -477-bp regions. The -217-bp promoter region regained promoter activity that approached the activity of the full-length promoter construct, suggesting that both positive and negative cis-acting regions may be involved in ameloblastin transcriptional regulation. Activity of the ameloblastin promoter in gingival and pulp fibroblasts was minimal and ranged from 8 to 30% of the activity in ameloblast-like cells. Several DNA-protein complexes were formed between functionally important promoter fragments and nuclear extracts from LS8 cells. The inactivity of promoter constructs in pulp and gingival fibroblasts as well as the absence of similar DNA-protein complexes from these cells suggest that regulatory regions of the murine ameloblastin promoter may function in a cell-specific manner.
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Affiliation(s)
- S Dhamija
- University of Michigan, School of Dentistry, Ann Arbor, Michigan 48109-1078, USA
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Fincham AG, Moradian-Oldak J, Simmer JP. The structural biology of the developing dental enamel matrix. J Struct Biol 1999; 126:270-99. [PMID: 10441532 DOI: 10.1006/jsbi.1999.4130] [Citation(s) in RCA: 474] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The biomineralization of the dental enamel matrix with a carbonated hydroxyapatite mineral generates one of the most remarkable examples of a vertebrate mineralized tissue. Recent advances in the molecular biology of ameloblast gene products have now revealed the primary structures of the principal proteins involved in this extracellular mineralizing system, amelogenins, tuftelins, ameloblastins, enamelins, and proteinases, but details of their secondary, tertiary, and quaternary structures, their interactions with other matrix and or cell surface proteins, and their functional role in dental enamel matrix mineralization are still largely unknown. This paper reviews our current knowledge of these molecules, the probable molecular structure of the enamel matrix, and the functional role of these extracellular matrix proteins. Recent studies on the major structural role played by the amelogenin proteins are discussed, and some new data on synthetic amelogenin matrices are reviewed.
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Affiliation(s)
- A G Fincham
- Center for Craniofacial Molecular Biology, School of Dentistry, Los Angeles, California 90089, USA
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