1
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Otake S, Saito K, Chiba Y, Yamada A, Fukumoto S. S100a6 knockdown promotes the differentiation of dental epithelial cells toward the epidermal lineage instead of the odontogenic lineage. FASEB J 2024; 38:e23608. [PMID: 38593315 DOI: 10.1096/fj.202302412rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 03/25/2024] [Accepted: 03/29/2024] [Indexed: 04/11/2024]
Abstract
Tooth development is a complex process involving various signaling pathways and genes. Recent findings suggest that ion channels and transporters, including the S100 family of calcium-binding proteins, may be involved in tooth formation. However, our knowledge in this regard is limited. Therefore, this study aimed to investigate the expression of S100 family members and their functions during tooth formation. Tooth germs were extracted from the embryonic and post-natal mice and the expression of S100a6 was examined. Additionally, the effects of S100a6 knockdown and calcium treatment on S100a6 expression and the proliferation of SF2 cells were examined. Microarrays and single-cell RNA-sequencing indicated that S100a6 was highly expressed in ameloblasts. Immunostaining of mouse tooth germs showed that S100a6 was expressed in ameloblasts but not in the undifferentiated dental epithelium. Additionally, S100a6 was localized to the calcification-forming side in enamel-forming ameloblasts. Moreover, siRNA-mediated S100a6 knockdown in ameloblasts reduced intracellular calcium concentration and the expression of ameloblast marker genes, indicating that S100a6 is associated with ameloblast differentiation. Furthermore, S100a6 knockdown inhibited the ERK/PI3K signaling pathway, suppressed ameloblast proliferation, and promoted the differentiation of the dental epithelium toward epidermal lineage. Conclusively, S100a6 knockdown in the dental epithelium suppresses cell proliferation via calcium and intracellular signaling and promotes differentiation of the dental epithelium toward the epidermal lineage.
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Grants
- 23H03109 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 21J21873 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 22H03296 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 22H00488 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 20K20612 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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Affiliation(s)
- Shinji Otake
- Division of Pediatric Dentistry, Department of Community Social Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Kan Saito
- Division of Pediatric Dentistry, Department of Community Social Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Yuta Chiba
- Division of Pediatric Dentistry, Department of Community Social Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Aya Yamada
- Division of Pediatric Dentistry, Department of Community Social Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Satoshi Fukumoto
- Division of Pediatric Dentistry, Department of Community Social Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
- Section of Pediatric Dentistry, Division of Oral Health, Growth and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
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2
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Souza Bomfim GH, Mitaishvili E, Schnetkamp PP, Lacruz RS. Na+/Ca2+ exchange in enamel cells is dominated by the K+-dependent NCKX exchanger. J Gen Physiol 2024; 156:e202313372. [PMID: 37947795 PMCID: PMC10637953 DOI: 10.1085/jgp.202313372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 08/15/2023] [Accepted: 10/31/2023] [Indexed: 11/12/2023] Open
Abstract
Calcium (Ca2+) extrusion is an essential function of the enamel-forming ameloblasts, providing Ca2+ for extracellular mineralization. The plasma membrane Ca2+ ATPases (PMCAs) remove cytosolic Ca2+ (cCa2+) and were recently shown to be efficient when ameloblasts experienced low cCa2+ elevation. Sodium-calcium (Na+/Ca2+) exchange has higher capacity to extrude cCa2+, but there is limited evidence on the function of the two main families of Na+/Ca2+ exchangers in enamel formation. The purpose of this study was to analyze the function of the NCX (coded by SLC8) and the K+-dependent NCKX (coded by SLC24) exchangers in rat ameloblasts and to compare their efficacy in the two main stages of enamel formation: the enamel forming secretory stage and the mineralizing or maturation stage. mRNA expression profiling confirmed the expression of Slc8 and Slc24 genes in enamel cells, Slc24a4 being the most highly upregulated transcript during the maturation stage, when Ca2+ transport increases. Na+/Ca2+ exchange was analyzed in the Ca2+ influx mode in Fura-2 AM-loaded ameloblasts. We show that maturation-stage ameloblasts have a higher Na+/Ca2+ exchange capacity than secretory-stage cells. We also show that Na+/Ca2+ exchange in both stages is dominated by NCKX over NCX. The importance of NCKX function in ameloblasts may partly explain why mutations in the SLC24A4 gene, but not in SLC8 genes, result in enamel disease. Our results demonstrate that Na+/Ca2+ exchangers are fully operational in ameloblasts and that their contribution to Ca2+ homeostasis increases in the maturation stage, when Ca2+ transport need is higher.
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Affiliation(s)
| | - Erna Mitaishvili
- Department of Chemistry, Herbert H. Lehman College, City University of New York. PhD Program in Biology, The Graduate Center of The City University of New York, New York, NY, USA
| | - Paul P.M. Schnetkamp
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Rodrigo S. Lacruz
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY, USA
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3
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Kim KH, Kim EJ, Kim HY, Li S, Jung HS. Fabrication of functional ameloblasts from hiPSCs for dental application. Front Cell Dev Biol 2023; 11:1164811. [PMID: 37457296 PMCID: PMC10339106 DOI: 10.3389/fcell.2023.1164811] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 06/15/2023] [Indexed: 07/18/2023] Open
Abstract
Tooth formation relies on two types of dental cell populations, namely, the dental epithelium and dental mesenchyme, and the interactions between these cell populations are important during tooth development. Although human-induced pluripotent stem cells (hiPSCs) can differentiate into dental epithelial and mesenchymal cells, organoid research on tooth development has not been established yet. This study focused on the hiPSC-derived human ameloblast organoid (hAO) using a three-dimensional (3D) culture system. hAOs had similar properties to ameloblasts, forming enamel in response to calcium and mineralization by interaction with the dental mesenchyme. hAOs simultaneously had osteogenic and odontogenic differentiation potential. Furthermore, hAOs demonstrated tooth regenerative potential upon interaction with the mouse dental mesenchyme. Our findings provide new insights into a suitable hiPSC-derived dental source and demonstrate that hAOs can be beneficial not only for tooth regeneration but also for the study of various dental diseases for which treatment has not been developed yet.
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Affiliation(s)
- Ka-Hwa Kim
- Division in Anatomy and Developmental Biology, Department of Oral Biology, Taste Research Center, Oral Science Research Center, BK21 FOUR Project, Yonsei University College of Dentistry, Seoul, Republic of Korea
| | - Eun-Jung Kim
- Division in Anatomy and Developmental Biology, Department of Oral Biology, Taste Research Center, Oral Science Research Center, BK21 FOUR Project, Yonsei University College of Dentistry, Seoul, Republic of Korea
| | | | - Shujin Li
- Division in Anatomy and Developmental Biology, Department of Oral Biology, Taste Research Center, Oral Science Research Center, BK21 FOUR Project, Yonsei University College of Dentistry, Seoul, Republic of Korea
| | - Han-Sung Jung
- Division in Anatomy and Developmental Biology, Department of Oral Biology, Taste Research Center, Oral Science Research Center, BK21 FOUR Project, Yonsei University College of Dentistry, Seoul, Republic of Korea
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4
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Transcriptomic Network Regulation of Rat Tooth Germ from Bell Differentiation Stage to Secretory Stage: MAPK Signaling Pathway Is Crucial to Extracellular Matrix Remodeling. BIOMED RESEARCH INTERNATIONAL 2023; 2023:4038278. [PMID: 36820224 PMCID: PMC9938770 DOI: 10.1155/2023/4038278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 12/30/2022] [Accepted: 01/05/2023] [Indexed: 02/13/2023]
Abstract
Hard tissues make up the vast majority of teeth and are mineralized from the surrounding matrix. If the development of tooth germ is affected during mineralization, hypoplasia of the tooth tissue can occur. To better understand the mechanisms mediating hypoplasia, we need to first study normal development. Using a rodent model, we highlight the transcriptomic changes that occur from the differentiation to secretion stages of mandibular molar germs. The tooth germ was dissected from rats at postnatal day 1.5 or 3.5 for high-throughput sequencing. Combining transcriptome analysis and DNA methylation, we identified 590 differentially expressed genes (436 upregulated and 154 downregulated) and 551 differentially expressed lncRNAs (long noncoding RNA; 369 upregulated and 182 downregulated) which were linked to the biological processes of odontogenesis, amelogenesis, tooth mineralization, and the alteration of extracellular matrix (ECM), especially matrix metalloproteinases (MMPs) and elastin. We found DNA methylation changes in 32 selected fragments involved in 5 chromosomes, 26 targets, and 2 haplotypes. Finally, three novel genes were identified: MMP20, Tgfb3, and Dusp1. Further analysis revealed that MMP20 has a role in odontogenesis and amelogenesis by influencing Slc24a4 and DSPP; Tgfb3 is involved in epithelial cell proliferation, cellular component disassembly process, ECM cellular component, and decomposition of cell components. But lncRNA expression could affect DNA methylation and mRNA expression. Moreover, the degree of DNA methylation could also affect the transcriptome level. Thus, Tgfb3 had no difference in DNA methylation, and Dusp1 conferred no difference at the transcriptome level. These three genes were all enriched in the MAPK pathway and played an important role in ECM remodeling. These data suggest that during the period of the bell differentiation stage to the secretory stage, along with enamel/dentin matrix secretion and hard tissue occurrence, the ECM is remodeled via MAPK signaling.
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5
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Souza Bomfim GH, Giacomello M, Lacruz RS. PMCA Ca 2+ clearance in dental enamel cells depends on the magnitude of cytosolic Ca 2. FASEB J 2023; 37:e22679. [PMID: 36515675 PMCID: PMC11006021 DOI: 10.1096/fj.202201291r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/31/2022] [Accepted: 11/21/2022] [Indexed: 12/15/2022]
Abstract
Enamel formation (amelogenesis) is a two-step process whereby crystals partially grow during the secretory stage followed by a significant growth expansion during the maturation stage concurrent with an increase in vectorial Ca2+ transport. This requires tight regulation of cytosolic Ca2+ (c Ca2+ ) concentration in the enamel forming ameloblasts by controlling Ca2+ influx (entry) and Ca2+ extrusion (clearance). Gene and protein expression studies suggest that the plasma membrane Ca2+ -ATPases (PMCA1-4) are likely involved in c Ca2+ extrusion in ameloblasts, yet no functional analysis of these pumps has been reported nor whether their activity changes across amelogenesis. PMCAs have high Ca2+ affinity and low Ca2+ clearance which may be a limiting factor in their contribution to enamel formation as maturation stage ameloblasts handle high Ca2+ loads. We analyzed PMCA function in rat secretory and maturation ameloblasts by blocking or potentiating these pumps. Low/moderate elevations in c Ca2+ measured using the Ca2+ probe Fura-2-AM show that secretory ameloblasts clear Ca2+ faster than maturation stage cells through PMCAs. This process was completely inhibited by an external alkaline (pH 9.0) solution or was significantly delayed by the PMCA blockers vanadate and caloxin 1b1. Eliciting higher c Ca2+ transients via the activation of the ORAI1 Ca2+ channel showed that the PMCAs of maturation ameloblasts were more efficient. Inhibiting PMCAs decreased the rate of Ca2+ influx via ORAI1 but potentiation with forskolin had no effect. Our findings suggest that PMCAs are functional Ca2+ pumps during amelogenesis regulating c Ca2+ upon low and/or moderate Ca2+ stimulus in secretory stage, thus participating in amelogenesis.
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Affiliation(s)
| | - Marta Giacomello
- Department of Biology, University of Padova, Padua, Italy
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Rodrigo S. Lacruz
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, New York, USA
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6
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Arai H, Inaba A, Ikezaki S, Kumakami-Sakano M, Azumane M, Ohshima H, Morikawa K, Harada H, Otsu K. Energy metabolic shift contributes to the phenotype modulation of maturation stage ameloblasts. Front Physiol 2022; 13:1062042. [PMID: 36523561 PMCID: PMC9745043 DOI: 10.3389/fphys.2022.1062042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 11/15/2022] [Indexed: 12/13/2023] Open
Abstract
Maturation stage ameloblasts (M-ABs) are responsible for terminal enamel mineralization in teeth and undergo characteristic cyclic changes in both morphology and function between ruffle-ended ameloblasts (RA) and smooth-ended ameloblasts (SA). Energy metabolism has recently emerged as a potential regulator of cell differentiation and fate decisions; however, its implication in M-ABs remains unclear. To elucidate the relationship between M-ABs and energy metabolism, we examined the expression pattern of energy metabolic enzymes in M-ABs of mouse incisors. Further, using the HAT7 cell line with M-AB characteristics, we designed experiments to induce an energy metabolic shift by changes in oxygen concentration. We revealed that RA preferentially utilizes oxidative phosphorylation, whereas SA depends on glycolysis-dominant energy metabolism in mouse incisors. In HAT7 cells, hypoxia induced an energy metabolic shift toward a more glycolytic-dominant state, and the energy metabolic shift reduced alkaline phosphatase (ALP) activity and calcium transport and deposition with a change in calcium-related gene expression, implying a phenotype shift from RA to SA. Taken together, these results indicate that the energy metabolic state is an important determinant of the RA/SA phenotype in M-ABs. This study sheds light on the biological significance of energy metabolism in governing M-ABs, providing a novel molecular basis for understanding enamel mineralization and elucidating the pathogenesis of enamel hypomineralization.
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Affiliation(s)
- Haruno Arai
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
- Division of Pediatric and Special Care Dentistry, Department of Oral Health Science, School of Dentistry, Iwate Medical University, Morioka, Japan
| | - Akira Inaba
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
- Division of Pediatric and Special Care Dentistry, Department of Oral Health Science, School of Dentistry, Iwate Medical University, Morioka, Japan
| | - Shojiro Ikezaki
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
| | - Mika Kumakami-Sakano
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
| | - Marii Azumane
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
- Division of Oral and Maxillofacial Surgery, Department of Reconstructive Oral and Maxillofacial Surgery, Iwate Medical University, Morioka, Japan
| | - Hayato Ohshima
- Division of Anatomy and Cell Biology of the Hard Tissue, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kazumasa Morikawa
- Division of Pediatric and Special Care Dentistry, Department of Oral Health Science, School of Dentistry, Iwate Medical University, Morioka, Japan
| | - Hidemitsu Harada
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
| | - Keishi Otsu
- Division of Developmental Biology and Regenerative Medicine, Department of Anatomy, Iwate Medical University, Yahaba, Japan
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7
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Mahdee AF, Ali AH, Gillespie JI. Structural and functional relations between the connective tissue and epithelium of enamel organ and their role during enamel maturation. J Mol Histol 2021; 52:975-989. [PMID: 34100179 DOI: 10.1007/s10735-021-09992-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/02/2021] [Indexed: 10/21/2022]
Abstract
The morphological and possible functional interactions between the connective tissue and enamel organ cells were examined during the maturation phase of enamel formation, using immunohistochemical techniques. Decalcified mandibular sections (10 µm) including incisors were used from Wistar rats ages 10-12 weeks. Sections were incubated with one or two primary antibodies targeting cell cytoskeleton (vimentin, α-actin, α-tubulin), dendritic marker (OX6), gap junctions (cx-43), enzymes (nitric-oxide synthase (nos1) and cyclooxygenase (cox1)), and the ion transporters (Na+/H+ exchanger (NHE1) and Na+/Ca2+ exchanger (NCX)) for 24 h, before incubation with the appropriate conjugated fluorescent secondary antibodies. Sections were examined by fluorescence microscopy. Haematoxylin-eosin slides were also employed. Cellular heterogeneity and morphological modulations were identified within enamel organ cells and connective tissue covering suggesting complex cellular interactions and indicating a new functional concept and possible complementary role during enamel maturation. Also, some ion transportation activity, and nos1 and cox1 signalling pathways have been identified, indicating intercellular communication between these regions. A hypothesis is suggested, to explain the morphological modulation of ameloblasts and papillary cells during enamel maturation which functions to increase the transporting membrane surface area to accomplish faster and bulker ion transportation to achieve controlled pH and to direct Ca2+ towards enamel.
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Affiliation(s)
- Anas F Mahdee
- Department of Restorative and Aesthetic Dentistry, College of Dentistry, University of Baghdad, Baghdad, Iraq.
| | - Ahmed H Ali
- Department of Restorative and Aesthetic Dentistry, College of Dentistry, University of Baghdad, Baghdad, Iraq
| | - James I Gillespie
- Department of Urology, Campus Drie Eiken, University of Antwerp, Antwerp, Belgium
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8
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Costiniti V, Bomfim GH, Mitaishvili E, Son GY, Li Y, Lacruz RS. Calcium Transport in Specialized Dental Epithelia and Its Modulation by Fluoride. Front Endocrinol (Lausanne) 2021; 12:730913. [PMID: 34456880 PMCID: PMC8385142 DOI: 10.3389/fendo.2021.730913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 07/26/2021] [Indexed: 11/25/2022] Open
Abstract
Most cells use calcium (Ca2+) as a second messenger to convey signals that affect a multitude of biological processes. The ability of Ca2+ to bind to proteins to alter their charge and conformation is essential to achieve its signaling role. Cytosolic Ca2+ (cCa2+) concentration is maintained low at ~100 nM so that the impact of elevations in cCa2+ is readily sensed and transduced by cells. However, such elevations in cCa2+ must be transient to prevent detrimental effects. Cells have developed a variety of systems to rapidly clear the excess of cCa2+ including Ca2+ pumps, exchangers and sequestering Ca2+ within intracellular organelles. This Ca2+ signaling toolkit is evolutionarily adapted so that each cell, tissue, and organ can fulfill its biological function optimally. One of the most specialized cells in mammals are the enamel forming cells, the ameloblasts, which also handle large quantities of Ca2+. The end goal of ameloblasts is to synthesize, secrete and mineralize a unique proteinaceous matrix without the benefit of remodeling or repair mechanisms. Ca2+ uptake into ameloblasts is mainly regulated by the store operated Ca2+ entry (SOCE) before it is transported across the polarized ameloblasts to reach the insulated enamel space. Here we review the ameloblasts Ca2+ signaling toolkit and address how the common electronegative non-metal fluoride can alter its function, potentially addressing the biology of dental fluorosis.
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Affiliation(s)
| | | | | | | | | | - Rodrigo S. Lacruz
- Department Molecular Pathobiology, College of Dentistry, New York University, New York, NY, United States
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9
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Boo MV, Chew SF, Ip YK. Basolateral Na +/Ca 2+ exchanger 1 and Na +/K +-ATPase, which display light-enhanced gene and protein expression levels, could be involved in the absorption of exogenous Ca 2+ through the ctenidium of the giant clam, Tridacna squamosa. Comp Biochem Physiol A Mol Integr Physiol 2021; 259:110997. [PMID: 34051370 DOI: 10.1016/j.cbpa.2021.110997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/22/2021] [Accepted: 05/24/2021] [Indexed: 10/21/2022]
Abstract
Giant clams perform light-enhanced shell formation (calcification) and therefore need to increase the uptake of exogenous Ca2+ during illumination. The ctenidium of the fluted giant clam, Tridacna squamosa, is involved in light-enhanced Ca2+ uptake. It expresses the pore-forming voltage-gated calcium channel (VGCC) subunit alpha 1 (CACNA1) in the apical membrane of the epithelial cells, and the protein expression level of CACNA1 is upregulated in the ctenidium during illumination. This study aimed to elucidate the mechanism involved in the transport of the absorbed Ca2+ across the basolateral membrane of the ctenidial epithelial cells into the hemolymph. We obtained a homolog of Na+/Ca2+exchanger 1 (NCX1-like) from the ctenidium of T. squamosa, which comprised 2418 bp, encoding a protein of 806 amino acids (88.9 kDa). NCX1-like had a basolateral localization in the epithelial cells of the ctenidial filaments and tertiary water channels. Illumination resulted in significant increases in the transcript and protein levels of NCX1-like/NCX1-like in the ctenidium. Hence, NCX1-like could operate in conjunction with VGCC to increase the transport of Ca2+ from the ambient seawater into the hemolymph during illumination. Illumination also resulted in the upregulation of the gene and protein expression levels of Na+/K+-ATPase (NKA) α-subunit (NKAα/NKAα) in the ctenidium of T. squamosa. As light-enhanced extrusion of Ca2+ into the hemolymph through NCX1-like would lead to a greater influx of extracellular Na+, the increased expression of the basolateral NKA was required to augment the capacity of intracellular Na+ homeostasis.
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Affiliation(s)
- Mel V Boo
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Republic of Singapore
| | - Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore.
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10
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Ji M, Xiao L, Xu L, Huang S, Zhang D. How pH is regulated during amelogenesis in dental fluorosis. Exp Ther Med 2018; 16:3759-3765. [PMID: 30402142 DOI: 10.3892/etm.2018.6728] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 12/01/2017] [Indexed: 12/14/2022] Open
Abstract
Amelogenesis is a complicated process that concerns the interaction between growing hydroxyapatite crystals and extracellular proteins, which requires the tight regulation of pH. In dental fluorosis, the balance of pH regulation is broken, leading to abnormal mineralization. The current review focuses on the electrolyte transport processes associated with pH homeostasis, particularly regarding the changes in ion transporters that occur during amelogenesis, following exposure to excessive fluoride. Furthermore, the possible mechanism of fluorosis is discussed on the basis of acid hypothesis. There are two main methods by which F- accelerates crystal formation in ameloblasts. Firstly, it induces the release of protons, lowering the pH of the cell microenvironment. The decreased pH stimulates the upregulation of ion transporters, which attenuates further declines in the pH. Secondly, F- triggers an unknown signaling pathway, causing changes in the transcription of ion transporters and upregulating the expression of bicarbonate transporters. This results in the release of a large amount of bicarbonate from ameloblasts, which may neutralize the pH to form a microenvironment that favors crystal nucleation. The decreased pH stimulates the diffusion of F- into the cytoplasm of amelobalsts along the concentration gradient formed by the release of protons. The retention of F- causes a series of pathological changes, including oxidative and endoplasmic reticulum stress. If the buffering capacity of ameloblasts facing F- toxicity holds, normal mineralization occurs; however, if F- levels are high enough to overwhelm the buffering capacity of ameloblasts, abnormal mineralization occurs, leading to dental fluorosis.
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Affiliation(s)
- Mei Ji
- Department of Stomatology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Lili Xiao
- Department of Stomatology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Le Xu
- Department of Stomatology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Shengyun Huang
- Department of Stomatology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Dongsheng Zhang
- Department of Stomatology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
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11
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An S. The emerging role of extracellular Ca
2+
in osteo/odontogenic differentiation and the involvement of intracellular Ca
2+
signaling: From osteoblastic cells to dental pulp cells and odontoblasts. J Cell Physiol 2018; 234:2169-2193. [DOI: 10.1002/jcp.27068] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 06/25/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Shaofeng An
- Department of Operative Dentistry and EndodonticsGuanghua School of Stomatology, Hospital of Stomatology, Sun Yat‐sen UniversityGuangzhou China
- Guangdong Province Key Laboratory of StomatologySun Yat‐Sen UniversityGuangzhou China
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12
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Kim HE, Hong JH. The overview of channels, transporters, and calcium signaling molecules during amelogenesis. Arch Oral Biol 2018; 93:47-55. [PMID: 29803993 DOI: 10.1016/j.archoralbio.2018.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 05/18/2018] [Accepted: 05/19/2018] [Indexed: 01/02/2023]
Abstract
Enamel is a highly calcified tissue. Its formation requires a progressive and dynamic system for the regulation of electrolyte concentration by enamel epithelia. A critical function of enamel epithelial cells, ameloblasts, is the secretion and movement of electrolytes via various channels and transporters to develop the enamel tissue. Enamel formation generates protons, which need to be neutralised. Thus, ameloblasts possess a buffering system to sustain mineral accretion. Normal tooth formation involves stage-dependent net fluctuations in pH during amelogenesis. To date, all of our information about ion transporters in dental enamel tissue is based solely on immunostaining-expression techniques. This review critically evaluates the current understanding and recent discoveries and physiological role of ion channels and transporters, Mg2+ transporters, and Ca2+ regulatory proteins during amelogenesis in enamel formation. The ways in which ameloblasts modulate ions are discussed in the context of current research for developing a novel morphologic-functional model of enamel maturation.
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Affiliation(s)
- Hee-Eun Kim
- Department of Dental Hygiene, College of Health Science, Gachon University, 191 Hambangmoe-ro, Yeonsu-gu, Incheon, 21936, South Korea
| | - Jeong Hee Hong
- Department of Physiology, College of Medicine, Lee Gil Ya Cancer and Diabetes Institute, GAIHST, Gachon University, Incheon, 21999, South Korea.
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13
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Eckstein M, Aulestia FJ, Nurbaeva MK, Lacruz RS. Altered Ca 2+ signaling in enamelopathies. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1778-1785. [PMID: 29750989 DOI: 10.1016/j.bbamcr.2018.04.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/26/2018] [Accepted: 04/30/2018] [Indexed: 10/16/2022]
Abstract
Biomineralization requires the controlled movement of ions across cell barriers to reach the sites of crystal growth. Mineral precipitation occurs in aqueous phases as fluids become supersaturated with specific ionic compositions. In the biological world, biomineralization is dominated by the presence of calcium (Ca2+) in crystal lattices. Ca2+ channels are intrinsic modulators of this process, facilitating the availability of Ca2+ within cells in a tightly regulated manner in time and space. Unequivocally, the most mineralized tissue produced by vertebrates, past and present, is dental enamel. With some of the longest carbonated hydroxyapatite (Hap) crystals known, dental enamel formation is fully coordinated by specialized epithelial cells of ectodermal origin known as ameloblasts. These cells form enamel in two main developmental stages: a) secretory; and b) maturation. The secretory stage is marked by volumetric growth of the tissue with limited mineralization, and the opposite is found in the maturation stage, as enamel crystals expand in width concomitant with increased ion transport. Disruptions in the formation and/or mineralization stages result, in most cases, in permanent alterations in the crystal assembly. This introduces weaknesses in the material properties affecting enamel's hardness and durability, thus limiting its efficacy as a biting, chewing tool and increasing the possibility of pathology. Here, we briefly review enamel development and discuss key properties of ameloblasts and their Ca2+-handling machinery, and how alterations in this toolkit result in enamelopathies.
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Affiliation(s)
- Miriam Eckstein
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, United States
| | - Francisco J Aulestia
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, United States
| | - Meerim K Nurbaeva
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, United States
| | - Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, United States.
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14
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Jalali R, Lodder JC, Zandieh-Doulabi B, Micha D, Melvin JE, Catalan MA, Mansvelder HD, DenBesten P, Bronckers A. The Role of Na:K:2Cl Cotransporter 1 (NKCC1/SLC12A2) in Dental Epithelium during Enamel Formation in Mice. Front Physiol 2017; 8:924. [PMID: 29209227 PMCID: PMC5702478 DOI: 10.3389/fphys.2017.00924] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 10/31/2017] [Indexed: 12/21/2022] Open
Abstract
Na+:K+:2Cl− cotransporters (NKCCs) belong to the SLC12A family of cation-coupled Cl− transporters. We investigated whether enamel-producing mouse ameloblasts express NKCCs. Transcripts for Nkcc1 were identified in the mouse dental epithelium by RT-qPCR and NKCC1 protein was immunolocalized in outer enamel epithelium and in the papillary layer but not the ameloblast layer. In incisors of Nkcc1-null mice late maturation ameloblasts were disorganized, shorter and the mineral density of the enamel was reduced by 10% compared to wild-type controls. Protein levels of gap junction protein connexin 43, Na+-dependent bicarbonate cotransporter e1 (NBCe1), and the Cl−-dependent bicarbonate exchangers SLC26A3 and SLC26A6 were upregulated in Nkcc1-null enamel organs while the level of NCKX4/SLC24A4, the major K+, Na+ dependent Ca2+ transporter in maturation ameloblasts, was slightly downregulated. Whole-cell voltage clamp studies on rat ameloblast-like HAT-7 cells indicated that bumetanide increased ion-channel activity conducting outward currents. Bumetanide also reduced cell volume of HAT-7 cells. We concluded that non-ameloblast dental epithelium expresses NKCC1 to regulate cell volume in enamel organ and provide ameloblasts with Na+, K+ and Cl− ions required for the transport of mineral- and bicarbonate-ions into enamel. Absence of functional Nkcc1 likely is compensated by other types of ion channels and ion transporters. The increased amount of Cx43 in enamel organ cells in Nkcc1-null mice suggests that these cells display a higher number of gap junctions to increase intercellular communication.
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Affiliation(s)
- Rozita Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam Movement Sciences, University of Amsterdam, VU University Amsterdam, Amsterdam, Netherlands.,Department of Functional Anatomy, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute Amsterdam, University of Amsterdam, VU University Amsterdam, Amsterdam, Netherlands
| | - Johannes C Lodder
- Department Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Behrouz Zandieh-Doulabi
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam Movement Sciences, University of Amsterdam, VU University Amsterdam, Amsterdam, Netherlands
| | - Dimitra Micha
- Department of Clinical Genetics, VU University Medical Center, Amsterdam Movement Sciences, Netherlands
| | - James E Melvin
- Secretory Mechanisms and Dysfunction Section, NIDCR/NIH, Bethesda, MD, United States
| | - Marcelo A Catalan
- Secretory Mechanisms and Dysfunction Section, NIDCR/NIH, Bethesda, MD, United States.,Departamento de Ciencias Químicas y Farmaceúticas, Facultad de Ciencias de la Salud, Universidad Arturo Prat, Iquique, Chile
| | - Huibert D Mansvelder
- Department Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Pamela DenBesten
- Department of Orofacial Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA, United States
| | - Antonius Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam Movement Sciences, University of Amsterdam, VU University Amsterdam, Amsterdam, Netherlands
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15
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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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16
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Furukawa Y, Haruyama N, Nikaido M, Nakanishi M, Ryu N, Oh-Hora M, Kuremoto K, Yoshizaki K, Takano Y, Takahashi I. Stim1 Regulates Enamel Mineralization and Ameloblast Modulation. J Dent Res 2017; 96:1422-1429. [PMID: 28732182 DOI: 10.1177/0022034517719872] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Loss-of-function mutations in the Ca2+ release-activated Ca2+ channel genes ORAI1 and STIM1 abolish store-operated Ca2+ entry (SOCE) and result in ectodermal dysplasia with amelogenesis imperfecta. However, because of the limited availability of patient tissue, analyses of enamel mineralization or possible changes in ameloblast function or morphology have not been possible. Here, we generated mice with ectodermal tissue-specific deletion of Stim1 ( Stim1 cKO [conditional knockout]), Stim2 ( Stim2 cKO), and Stim1 and Stim2 ( Stim1/2 cKO) and analyzed their enamel phenotypes as compared with those of control ( Stim1/2fl/fl) animals. Ablation of Stim1 and Stim1/2 but not Stim2 expression resulted in chalky enamel and severe attrition at the incisor tips and molar cusps. Stim1 and Stim1/2 cKO, but not Stim2 cKO, demonstrated inferior enamel mineralization with impaired structural integrity, whereas the shape of the teeth and enamel thickness appeared to be normal in all animals. The gene expression levels of the enamel matrix proteins Amelx and Ambn and the enamel matrix proteases Mmp20 and Klk4 were not altered by the abrogation of SOCE in Stim1/2 cKO mice. The morphology of ameloblasts during the secretory and maturation stages was not significantly altered in either the incisors or molars of the cKO animals. However, in Stim1 and Stim1/2 cKO incisors, the alternating modulation of maturation-stage ameloblasts between the smooth- and ruffle-ended cell types continued beyond the regular cycle and extended to the areas corresponding to the zone of postmodulation ameloblasts in the teeth of control animals. These results indicate that SOCE is essential for proper enamel mineralization, in which Stim1 plays a critical role during the maturation process.
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Affiliation(s)
- Y Furukawa
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.,2 Institute of Decision Science Program for Sustainable Society, Kyushu University, Fukuoka, Japan
| | - N Haruyama
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - M Nikaido
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - M Nakanishi
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - N Ryu
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - M Oh-Hora
- 3 Division of Molecular Immunology, Research Center for Infectious Diseases, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - K Kuremoto
- 4 Department of Advanced Prosthodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - K Yoshizaki
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Y Takano
- 5 Department of Cell Biology and Neuroscience, School of Medicine, Juntendo University, Tokyo, Japan
| | - I Takahashi
- 1 Section of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
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17
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Lacruz RS. Enamel: Molecular identity of its transepithelial ion transport system. Cell Calcium 2017; 65:1-7. [PMID: 28389033 PMCID: PMC5944837 DOI: 10.1016/j.ceca.2017.03.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 03/27/2017] [Accepted: 03/27/2017] [Indexed: 12/14/2022]
Abstract
Enamel is the most calcified tissue in vertebrates. It differs from bone in a number of characteristics including its origin from ectodermal epithelium, lack of remodeling capacity by the enamel forming cells, and absence of collagen. The enamel-forming cells known as ameloblasts, choreograph first the synthesis of a unique protein-rich matrix, followed by the mineralization of this matrix into a tissue that is ∼95% mineral. To do this, ameloblasts arrange the coordinated movement of ions across a cell barrier while removing matrix proteins and monitoring extracellular pH using a variety of buffering systems to enable the growth of carbonated apatite crystals. Although our knowledge of these processes and the molecular identity of the proteins involved in transepithelial ion transport has increased in the last decade, it remains limited compared to other cells. Here we present an overview of the evolution and development of enamel, its differences with bone, and describe the ion transport systems associated with ameloblasts.
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Affiliation(s)
- Rodrigo S Lacruz
- Dept. Basic Science and Craniofacial Biology, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, United States.
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18
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Robertson SYT, Wen X, Yin K, Chen J, Smith CE, Paine ML. Multiple Calcium Export Exchangers and Pumps Are a Prominent Feature of Enamel Organ Cells. Front Physiol 2017; 8:336. [PMID: 28588505 PMCID: PMC5440769 DOI: 10.3389/fphys.2017.00336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/08/2017] [Indexed: 12/11/2022] Open
Abstract
Calcium export is a key function for the enamel organ during all stages of amelogenesis. Expression of a number of ATPase calcium transporting, plasma membrane genes (ATP2B1-4/PMCA1-4), solute carrier SLC8A genes (sodium/calcium exchanger or NCX1-3), and SLC24A gene family members (sodium/potassium/calcium exchanger or NCKX1-6) have been investigated in the developing enamel organ in earlier studies. This paper reviews the calcium export pathways that have been described and adds novel insights to the spatiotemporal expression patterns of PMCA1, PMCA4, and NCKX3 during amelogenesis. New data are presented to show the mRNA expression profiles for the four Atp2b1-4 gene family members (PMCA1-4) in secretory-stage and maturation-stage rat enamel organs. These data are compared to expression profiles for all Slc8a and Slc24a gene family members. PMCA1, PMCA4, and NCKX3 immunolocalization data is also presented. Gene expression profiles quantitated by real time PCR show that: (1) PMCA1, 3, and 4, and NCKX3 are most highly expressed during secretory-stage amelogenesis; (2) NCX1 and 3, and NCKX6 are expressed during secretory and maturation stages; (3) NCKX4 is most highly expressed during maturation-stage amelogenesis; and (4) expression levels of PMCA2, NCX2, NCKX1, NCKX2, and NCKX5 are negligible throughout amelogenesis. In the enamel organ PMCA1 localizes to the basolateral membrane of both secretory and maturation ameloblasts; PMCA4 expression is seen in the basolateral membrane of secretory and maturation ameloblasts, and also cells of the stratum intermedium and papillary layer; while NCKX3 expression is limited to Tomes' processes, and the apical membrane of maturation-stage ameloblasts. These new findings are discussed in the perspective of data already present in the literature, and highlight the multiplicity of calcium export systems in the enamel organ needed to regulate biomineralization.
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Affiliation(s)
- Sarah Y T Robertson
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern CaliforniaLos Angeles, CA, United States
| | - Xin Wen
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern CaliforniaLos Angeles, CA, United States
| | - Kaifeng Yin
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern CaliforniaLos Angeles, CA, United States
| | - Junjun Chen
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern CaliforniaLos Angeles, CA, United States.,Department of Oral Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of MedicineShanghai, China.,Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Department of Biochemistry and Molecular Cell Biology, Shanghai Jiao Tong University School of MedicineShanghai, China
| | - Charles E Smith
- Department of Anatomy and Cell Biology, Faculty of Medicine, McGill UniversityMontreal, QC, Canada
| | - Michael L Paine
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern CaliforniaLos Angeles, CA, United States
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19
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Nurbaeva MK, Eckstein M, Feske S, Lacruz RS. Ca 2+ transport and signalling in enamel cells. J Physiol 2017; 595:3015-3039. [PMID: 27510811 PMCID: PMC5430215 DOI: 10.1113/jp272775] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/21/2016] [Indexed: 01/02/2023] Open
Abstract
Dental enamel is one of the most remarkable examples of matrix-mediated biomineralization. Enamel crystals form de novo in a rich extracellular environment in a stage-dependent manner producing complex microstructural patterns that are visually stunning. This process is orchestrated by specialized epithelial cells known as ameloblasts which themselves undergo striking morphological changes, switching function from a secretory role to a cell primarily engaged in ionic transport. Ameloblasts are supported by a host of cell types which combined represent the enamel organ. Fully mineralized enamel is the hardest tissue found in vertebrates owing its properties partly to the unique mixture of ionic species represented and their highly organized assembly in the crystal lattice. Among the main elements found in enamel, Ca2+ is the most abundant ion, yet how ameloblasts modulate Ca2+ dynamics remains poorly known. This review describes previously proposed models for passive and active Ca2+ transport, the intracellular Ca2+ buffering systems expressed in ameloblasts and provides an up-dated view of current models concerning Ca2+ influx and extrusion mechanisms, where most of the recent advances have been made. We also advance a new model for Ca2+ transport by the enamel organ.
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Affiliation(s)
- Meerim K. Nurbaeva
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
| | - Miriam Eckstein
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
| | - Stefan Feske
- Department of PathologyNew York University School of MedicineNew YorkNY10016USA
| | - Rodrigo S. Lacruz
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
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20
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Xiang W, Liao W, Yi Z, He X, Ding Y. 25-Hydroxyvitamin D-1-α-hydroxylase in apoliporotein E knockout mice: The role of protecting vascular smooth muscle cell from calcification. Biomed Pharmacother 2017; 88:971-977. [PMID: 28178628 DOI: 10.1016/j.biopha.2017.01.093] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Revised: 01/11/2017] [Accepted: 01/15/2017] [Indexed: 02/02/2023] Open
Abstract
Previous publications widely reported that 25-hydroxyvitamin D-1-α-hydroxylase (CYP27B1) regulated the metabolism of 25-hydroxyvitamin D3, which has a close association between altered activity of vitamin D and vascular calcification has been reported in various human diseases, including chronic kidney disease, osteoporosis and atherosclerosis. Vascular calcification is a clinically significant component of atherosclerosis and may be promoted by ROS associated inflammatory. In this study, we evaluated the effect of 25-hydroxyvitamin D-1-α-hydroxylase on the atherosclerosis disease both in apolipoprotein (apo) E-/- mice and wild-type mice. We also isolated endothelial cell (ECs) and vascular smooth muscle cells (VSMCs) in aortic from the wild type mice and apoE-/- mice respectively, then investigated that after parathyroid hormone (PTH) both of the CYP27B1 and vitamin D receptor (VDR) expressions in apoE-/-EC and apoE-/-VSMC were higher than the wide-type EC and VSMCs. However, the increased proliferation and decreased apoptosis have showed in EC and VSMC compared with the cells from apo E-/- mice. Moreover, the index associated with vascular calcification such as intracellular Ca2+ concentration and alkaline phosphatase (ALP) activity have been tested and the result suggested that the levels of the former index have improved in the apoE-/-EC and apoE-/-VSMC. We got similar conclusions under the pre-treatment with 1, 25(OH) 2D3.
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Affiliation(s)
- Wei Xiang
- Department of Pediatrics, Hainan General Hospital, Haikou 570102, China; Department of Pediatrics, Maternal and Child Health care Hospital of Hainan Province, Haikou 570206, China
| | - Wang Liao
- Department of Cardiology, Hainan General Hospital, Haikou 570102, China
| | - Zhuwen Yi
- Department of Nephropathy, Children's Medical Center, The Second Xiangya Hospital, Central South University, Changsha, 410000, China
| | - Xiaojie He
- Department of Nephropathy, Children's Medical Center, The Second Xiangya Hospital, Central South University, Changsha, 410000, China.
| | - Yan Ding
- Department of Dermatology, Maternal and Child Health care Hospital of Hainan Province,15 Long Kun-Nan Road, Haikou 570206, China.
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21
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Bronckers ALJJ, Jalali R, Lytton J. Reduced Protein Expression of the Na +/Ca 2++K +-Exchanger (SLC24A4) in Apical Plasma Membranes of Maturation Ameloblasts of Fluorotic Mice. Calcif Tissue Int 2017; 100:80-86. [PMID: 27752731 PMCID: PMC5215084 DOI: 10.1007/s00223-016-0197-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 10/03/2016] [Indexed: 02/07/2023]
Abstract
Exposure of forming enamel to fluoride results into formation of hypomineralized enamel. We tested whether enamel hypomineralization was caused by lower expression of the NCKX4/SLC24A4 Ca2+-transporter by ameloblasts. Three commercial antibodies against NCKX4 were tested on enamel organs of wild-type and Nckx4-null mice, one of which (a mouse monoclonal) was specific. This antibody gave a prominent staining of the apical plasma membranes of maturation ameloblasts, starting at early maturation. The layer of immuno-positive ameloblasts contained narrow gaps without immunostaining or with reduced staining. In fluorotic mouse incisors, the quantity of NCKX4 protein in ameloblasts as assessed by western blotting was not different from that in non-fluorotic ameloblasts. However, immunostaining of the apical plasma membranes of fluorotic ameloblasts was strongly reduced or absent suggesting that trafficking of NCKX4 to the apical membrane was strongly reduced. Exposure to fluoride may reduce NCKX4-mediated transport of Ca2+ by maturation stage ameloblasts which delays ameloblast modulation and reduces enamel mineralization.
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Affiliation(s)
- A L J J Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA, Amsterdam, The Netherlands.
| | - R Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), MOVE Research Institute, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA, Amsterdam, The Netherlands
| | - J Lytton
- Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4Z6, Canada
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22
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Abstract
Hypomineralization of developing enamel is associated with changes in ameloblast modulation during the maturation stage. Modulation (or pH cycling) involves the cyclic transformation of ruffle-ended (RE) ameloblasts facing slightly acidic enamel into smooth-ended (SE) ameloblasts near pH-neutral enamel. The mechanism of ameloblast modulation is not clear. Failure of ameloblasts of Cftr-null and anion exchanger 2 ( Ae2)-null mice to transport Cl- into enamel acidifies enamel, prevents modulation, and reduces mineralization. It suggests that pH regulation is critical for modulation and for completion of enamel mineralization. This report presents a review of the major types of transmembrane molecules that ameloblasts express to transport calcium to form crystals and bicarbonates to regulate pH. The type of transporter depends on the developmental stage. Modulation is proposed to be driven by the pH of enamel fluid and the compositional and/or physicochemical changes that result from increased acidity, which may turn RE ameloblasts into SE mode. Amelogenins delay outgrowth of crystals and keep the intercrystalline space open for diffusion of mineral ions into complete depth of enamel. Modulation enables stepwise removal of amelogenins from the crystal surface, their degradation, and removal from the enamel. Removal of matrix allows slow expansion of crystals. Modulation also reduces the stress that ameloblasts experience when exposed to high acid levels generated by mineral formation or by increased intracellular Ca2+. By cyclically interrupting Ca2+ transport by RE ameloblasts and their transformation into SE ameloblasts, proton production ceases shortly and enables the ameloblasts to recover. Modulation also improves enamel crystal quality by selectively dissolving immature Ca2+-poor crystals, removing impurities as Mg2+ and carbonates, and recrystallizing into more acid-resistant crystals.
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Affiliation(s)
- A L J J Bronckers
- 1 Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Amsterdam, Netherlands
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23
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Sun F, Cao Y, Yu C, Wei X, Yao J. 1,25-Dihydroxyvitamin D3 modulates calcium transport in goat mammary epithelial cells in a dose- and energy-dependent manner. J Anim Sci Biotechnol 2016; 7:41. [PMID: 27471592 PMCID: PMC4964070 DOI: 10.1186/s40104-016-0101-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 07/12/2016] [Indexed: 12/14/2022] Open
Abstract
Background Calcium is a vital mineral and an indispensable component of milk for ruminants. The regulation of transcellular calcium transport by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3, the active form of vitamin D) has been confirmed in humans and rodents, and regulators, including vitamin D receptor (VDR), calcium binding protein D9k (calbindin-D9k), plasma membrane Ca2+-ATPase 1b (PMCA1b), PMAC2b and Orai1, are involved in this process. However, it is still unclear whether 1,25-(OH)2D3 could stimulate calcium transport in the ruminant mammary gland. The present trials were conducted to study the effect of 1,25-(OH)2D3 supplementation and energy availability on the expression of genes and proteins related to calcium secretion in goat mammary epithelial cells. Methods An in vitro culture method for goat secreting mammary epithelial cells was successfully established. The cells were treated with different doses of 1,25-(OH)2D3 (0, 0.1, 1.0, 10.0 and 100.0 nmol/L) for calcium transport research, followed by a 3-bromopyruvate (3-BrPA, an inhibitor of glucose metabolism) treatment to determine its dependence on glucose availability. Cell proliferation ratios, glucose consumption and enzyme activities were measured with commercial kits, and real-time quantitative polymerase chain reaction (RT-qPCR), and western blots were used to determine the expression of genes and proteins associated with mammary calcium transport in dairy goats, respectively. Results 1,25-(OH)2D3 promoted cell proliferation and the expression of genes involved in calcium transport in a dose-dependent manner when the concentration did not exceed 10.0 nmol/L. In addition, 100.0 nmol/L 1,25-(OH)2D3 inhibited cell proliferation and the expression of associated genes compared with the 10.0 nmol/L treatment. The inhibition of hexokinase 2 (HK2), a rate-limiting enzyme in glucose metabolism, decreased the expression of PMCA1b and PMCA2b at the mRNA and protein levels as well as the transcription of Orai1, indicating that glucose availability was required for goat mammary calcium transport. The optimal concentration of 1,25-(OH)2D3 that facilitated calcium transport in this study was 10.0 nmol/L. Conclusions Supplementation with 1,25-(OH)2D3 influenced cell proliferation and regulated the expression of calcium transport modulators in a dose- and energy-dependent manner, thereby highlighting the role of 1,25-(OH)2D3 as an efficacious regulatory agent that produces calcium-enriched milk in ruminants when a suitable energy status was guaranteed.
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Affiliation(s)
- Feifei Sun
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 Shaanxi Peoples Republic of China
| | - Yangchun Cao
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 Shaanxi Peoples Republic of China
| | - Chao Yu
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 Shaanxi Peoples Republic of China
| | - Xiaoshi Wei
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 Shaanxi Peoples Republic of China
| | - Junhu Yao
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100 Shaanxi Peoples Republic of China
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Jalloul AH, Rogasevskaia TP, Szerencsei RT, Schnetkamp PPM. A Functional Study of Mutations in K+-dependent Na+-Ca2+ Exchangers Associated with Amelogenesis Imperfecta and Non-syndromic Oculocutaneous Albinism. J Biol Chem 2016; 291:13113-23. [PMID: 27129268 DOI: 10.1074/jbc.m116.728824] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 12/20/2022] Open
Abstract
K(+)-dependent Na(+)/Ca(2+) exchangers belong to the solute carrier 24 (SLC24A1-5) gene family of membrane transporters. Five different gene products (NCKX1-5) have been identified in humans, which play key roles in biological processes including vision, olfaction, and skin pigmentation. NCKXs are bi-directional membrane transporters that transport 1 Ca(2+)+K(+) ions in exchange for 4 Na(+) ions. Recent studies have linked mutations in the SLC24A4 (NCKX4) and SLC24A5 (NCKX5) genes to amylogenesis imperfecta (AI) and non-syndromic oculocutaneous albinism (OCA6), respectively. Here, we introduced mutations found in patients with AI and OCA6 into human SLC24A4 (NCKX4) cDNA leading to single residue substitutions in the mutant NCKX4 proteins. We measured NCKX-mediated Ca(2+) transport activity of WT and mutant NCKX4 proteins expressed in HEK293 cells. Three mutant NCKX4 cDNAs represent mutations found in the SCL24A4 gene and three represent mutations found in the SCL24A5 gene involving residues conserved between NCKX4 and NCKX5. Five mutant proteins had no observable NCKX activity, whereas one mutation resulted in a 78% reduction in transport activity. Total protein expression and trafficking to the plasma membrane (the latter with one exception) were not affected in the HEK293 cell expression system. We also analyzed two mutations in a Drosophila NCKX gene that have been reported to result in an increased susceptibility for seizures, and found that both resulted in mutant proteins with significantly reduced but observable NCKX activity. The data presented here support the genetic analyses that mutations in SLC24A4 and SLC24A5 are responsible for the phenotypic defects observed in human patients.
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Affiliation(s)
- Ali H Jalloul
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Tatiana P Rogasevskaia
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Robert T Szerencsei
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Paul P M Schnetkamp
- From the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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25
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Dental enamel cells express functional SOCE channels. Sci Rep 2015; 5:15803. [PMID: 26515404 PMCID: PMC4626795 DOI: 10.1038/srep15803] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 10/06/2015] [Indexed: 12/14/2022] Open
Abstract
Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.
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Abstract
Ca(2+) release-activated Ca(2+) (CRAC) channels mediate a specific form of Ca(2+) influx called store-operated Ca(2+) entry (SOCE) that contributes to the function of many cell types. CRAC channels are composed of ORAI1 proteins located in the plasma membrane, which form its ion-conducting pore. ORAI1 channels are activated by stromal interaction molecule (STIM) 1 and STIM2 located in the endoplasmic reticulum. Loss- and gain-of-function gene mutations in ORAI1 and STIM1 in human patients cause distinct disease syndromes. CRAC channelopathy is caused by loss-of-function mutations in ORAI1 and STIM1 that abolish CRAC channel function and SOCE; it is characterized by severe combined immunodeficiency (SCID)-like disease, autoimmunity, muscular hypotonia, and ectodermal dysplasia, with defects in sweat gland function and dental enamel formation. The latter defect emphasizes an important role of CRAC channels in tooth development. By contrast, autosomal dominant gain-of-function mutations in ORAI1 and STIM1 result in constitutive CRAC channel activation, SOCE, and increased intracellular Ca(2+) levels that are associated with an overlapping spectrum of diseases, including nonsyndromic tubular aggregate myopathy (TAM) and York platelet and Stormorken syndromes. The latter two syndromes are defined, besides myopathy, by thrombocytopenia, thrombopathy, and bleeding diathesis. The fact that myopathy results from both loss- and gain-of-function mutations in ORAI1 and STIM1 highlights the importance of CRAC channels for Ca(2+) homeostasis in skeletal muscle function. The cellular dysfunction and clinical disease spectrum observed in mutant patients provide important information about the molecular regulation of ORAI1 and STIM1 proteins and the role of CRAC channels in human physiology.
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Affiliation(s)
- Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York
| | - Stefan Feske
- Department of Pathology, New York University School of Medicine, New York, New York
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27
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Bronckers ALJJ, Lyaruu D, Jalali R, Medina JF, Zandieh-Doulabi B, DenBesten PK. Ameloblast Modulation and Transport of Cl⁻, Na⁺, and K⁺ during Amelogenesis. J Dent Res 2015; 94:1740-7. [PMID: 26403673 DOI: 10.1177/0022034515606900] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Ameloblasts express transmembrane proteins for transport of mineral ions and regulation of pH in the enamel space. Two major transporters recently identified in ameloblasts are the Na(+)K(+)-dependent calcium transporter NCKX4 and the Na(+)-dependent HPO4 (2-) (Pi) cotransporter NaPi-2b. To regulate pH, ameloblasts express anion exchanger 2 (Ae2a,b), chloride channel Cftr, and amelogenins that can bind protons. Exposure to fluoride or null mutation of Cftr, Ae2a,b, or Amelx each results in formation of hypomineralized enamel. We hypothesized that enamel hypomineralization associated with disturbed pH regulation results from reduced ion transport by NCKX4 and NaPi-2b. This was tested by correlation analyses among the levels of Ca, Pi, Cl, Na, and K in forming enamel of mice with null mutation of Cftr, Ae2a,b, and Amelx, according to quantitative x-ray electron probe microanalysis. Immunohistochemistry, polymerase chain reaction analysis, and Western blotting confirmed the presence of apical NaPi-2b and Nckx4 in maturation-stage ameloblasts. In wild-type mice, K levels in enamel were negatively correlated with Ca and Cl but less negatively or even positively in fluorotic enamel. Na did not correlate with P or Ca in enamel of wild-type mice but showed strong positive correlation in fluorotic and nonfluorotic Ae2a,b- and Cftr-null enamel. In hypomineralizing enamel of all models tested, 1) Cl(-) was strongly reduced; 2) K(+) and Na(+) accumulated (Na(+) not in Amelx-null enamel); and 3) modulation was delayed or blocked. These results suggest that a Na(+)K(+)-dependent calcium transporter (likely NCKX4) and a Na(+)-dependent Pi transporter (potentially NaPi-2b) located in ruffle-ended ameloblasts operate in a coordinated way with the pH-regulating machinery to transport Ca(2+), Pi, and bicarbonate into maturation-stage enamel. Acidification and/or associated physicochemical/electrochemical changes in ion levels in enamel fluid near the apical ameloblast membrane may reduce the transport activity of mineral transporters, which results in hypomineralization.
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Affiliation(s)
- A L J J Bronckers
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - D Lyaruu
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - R Jalali
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - J F Medina
- Division of Gene Therapy and Hepatology, School of Medicine/CIMA, University of Navarra, and CIBERehd, Pamplona, Spain
| | - B Zandieh-Doulabi
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam, University of Amsterdam, and MOVE Research Institute, VU University Amsterdam, Amsterdam, Netherlands
| | - P K DenBesten
- Department of Oral Sciences, University of California, San Francisco, CA, USA
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28
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Nurbaeva MK, Eckstein M, Snead ML, Feske S, Lacruz RS. Store-operated Ca2+ Entry Modulates the Expression of Enamel Genes. J Dent Res 2015; 94:1471-7. [PMID: 26232387 DOI: 10.1177/0022034515598144] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Dental enamel formation is an intricate process tightly regulated by ameloblast cells. The correct spatiotemporal patterning of enamel matrix protein (EMP) expression is fundamental to orchestrate the formation of enamel crystals, which depend on a robust supply of Ca2+. In the extracellular milieu, Ca2+ -EMP interactions occur at different levels. Despite its recognized role in enamel development, the molecular machinery involved in Ca2+ homeostasis in ameloblasts remains poorly understood. A common mechanism for Ca2+ influx is store-operated Ca2+ entry (SOCE). We evaluated the possibility that Ca2+ influx in enamel cells might be mediated by SOCE and the Ca2+ release-activated Ca2+ (CRAC) channel, the prototypical SOCE channel. Using ameloblast-like LS8 cells, we demonstrate that these cells express Ca2+ -handling molecules and mediate Ca2+ influx through SOCE. As a rise in the cytosolic Ca2+ concentration is a versatile signal that can modulate gene expression, we assessed whether SOCE in enamel cells had any effect on the expression of EMPs. Our results demonstrate that stimulating LS8 cells or murine primary enamel organ cells with thapsigargin to activate SOCE leads to increased expression of Amelx, Ambn, Enam, Mmp20. This effect is reversed when cells are treated with a CRAC channel inhibitor. These data indicate that Ca2+ influx in LS8 cells and enamel organ cells is mediated by CRAC channels and that Ca2+ signals enhance the expression of EMPs. Ca2+ plays an important role not only in mineralizing dental enamel but also in regulating the expression of EMPs.
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Affiliation(s)
- M K Nurbaeva
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY, USA
| | - M Eckstein
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY, USA
| | - M L Snead
- Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
| | - S Feske
- Department of Pathology, NYU School of Medicine, New York, NY, USA
| | - R S Lacruz
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY, USA
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29
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Varga G, Kerémi B, Bori E, Földes A. Function and repair of dental enamel - Potential role of epithelial transport processes of ameloblasts. Pancreatology 2015; 15:S55-60. [PMID: 25747281 DOI: 10.1016/j.pan.2015.01.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/28/2015] [Indexed: 12/11/2022]
Abstract
The hardest mammalian tissue, dental enamel is produced by ameloblasts, which are electrolyte-transporting epithelial cells. Although the end product is very different, they show many similarities to transporting epithelia of the pancreas, salivary glands and kidney. Enamel is produced in a multi-step epithelial secretory process that features biomineralization which is an interplay of secreted ameloblast specific proteins and the time-specific transport of minerals, protons and bicarbonate. First, "secretory" ameloblasts form the entire thickness of the enamel layer, but with low mineral content. Then they differentiate into "maturation" ameloblasts, which remove organic matrix from the enamel and in turn further build up hydroxyapatite crystals. The protons generated by hydroxyapatite formation need to be buffered, otherwise enamel will not attain full mineralization. Buffering requires a tight pH regulation and secretion of bicarbonate by ameloblasts. The whole process has been the focus of many immunohistochemical and gene knock-out studies, but, perhaps surprisingly, no functional data existed for mineral ion transport by ameloblasts. However, recent studies including ours provided a better insight for molecular mechanism of mineral formation. The secretory regulation is not completely known as yet, but its significance is crucial. Impairing regulation retards or prevents completion of enamel mineralization and results in the development of hypomineralized enamel that easily erodes after dental eruption. Factors that impair this function are fluoride and disruption of pH regulators. Revealing these factors may eventually lead to the treatment of enamel hypomineralization related to genetic or environmentally induced malformation.
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Affiliation(s)
- Gábor Varga
- Department of Oral Biology, Semmelweis University, Budapest, Hungary.
| | - Beáta Kerémi
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
| | - Erzsébet Bori
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
| | - Anna Földes
- Department of Oral Biology, Semmelweis University, Budapest, Hungary
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30
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Towards Understanding the Role of the Na+-Ca2+ Exchanger Isoform 3. Rev Physiol Biochem Pharmacol 2015; 168:31-57. [DOI: 10.1007/112_2015_23] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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31
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Wang S, Choi M, Richardson AS, Reid BM, Seymen F, Yildirim M, Tuna E, Gençay K, Simmer JP, Hu JC. STIM1 and SLC24A4 Are Critical for Enamel Maturation. J Dent Res 2014; 93:94S-100S. [PMID: 24621671 PMCID: PMC4107542 DOI: 10.1177/0022034514527971] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Dental enamel formation depends upon the transcellular transport of Ca(2+) by ameloblasts, but little is known about the molecular mechanism, or even if the same process is operative during the secretory and maturation stages of amelogenesis. Identifying mutations in genes involved in Ca(2+) homeostasis that cause inherited enamel defects can provide insights into the molecular participants and potential mechanisms of Ca(2+) handling by ameloblasts. Stromal Interaction Molecule 1 (STIM1) is an ER transmembrane protein that activates membrane-specific Ca(2+) influx in response to the depletion of ER Ca(2+) stores. Solute carrier family 24, member 4 (SLC24A4), is a Na(+)/K(+)/Ca(2+) transporter that exchanges intracellular Ca(2+) and K(+) for extracellular Na(+). We identified a proband with syndromic hypomaturation enamel defects caused by a homozygous C to T transition (g.232598C>T c.1276C>T p.Arg426Cys) in STIM1, and a proband with isolated hypomaturation enamel defects caused by a homozygous C to T transition (g.124552C>T; c.437C>T; p.Ala146Val) in SLC24A4. Immunohistochemistry of developing mouse molars and incisors showed positive STIM1 and SLC24A4 signal specifically in maturation-stage ameloblasts. We conclude that enamel maturation is dependent upon STIM1 and SLC24A4 function, and that there are important differences in the Ca(2+) transcellular transport systems used by secretory- and maturation-stage ameloblasts.
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Affiliation(s)
- S Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA Oral Health Sciences Program, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, USA
| | - M Choi
- Department of Biomedical Sciences, College of Medicine, Seoul National University, 275-1 Yongon-dong, Chongno-gu, Seoul 110-768, Korea Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, USA
| | - A S Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - B M Reid
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - F Seymen
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - M Yildirim
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - E Tuna
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - K Gençay
- Department of Pedodontics, Istanbul University, Faculty of Dentistry, Istanbul, Turkey
| | - J P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
| | - J C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, MI, USA
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32
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Wen X, Lacruz RS, Smith CE, Paine ML. Gene-expression profile and localization of Na+/K(+)-ATPase in rat enamel organ cells. Eur J Oral Sci 2013; 122:21-6. [PMID: 24313748 DOI: 10.1111/eos.12106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2013] [Indexed: 11/30/2022]
Abstract
The sodium pump Na(+)/K(+)-ATPase, expressed in virtually all cells of higher organisms, is involved in establishing a resting membrane potential and in creating a sodium gradient to facilitate a number of membrane-associated transport activities. Na(+)/K(+)-ATPase is an oligomer of α, β, and γ subunits. Four unique genes encode each of the α and β subunits. In dental enamel cells, the spatiotemporal expression of Na(+)/K(+)-ATPase is poorly characterized. Using the rat incisor as a model, this study provides a comprehensive expression profile of all four α and all four β Na(+)/K(+)-ATPase subunits throughout all stages of amelogenesis. Real-time PCR, western blot analysis, and immunolocalization revealed that α1, β1, and β3 are expressed in the enamel organ and that all three are most highly expressed during late-maturation-stage amelogenesis. Expression of β3 was significantly higher than expression of β1, suggesting that the dominant Na(+)/K(+)-ATPase consists of an α1β3 dimer. Localization of α1, β1, and β3 subunits in ameloblasts was primarily to the cytoplasm and occasionally along the basolateral membranes. Weaker expression was also noted in papillary layer cells during early maturation. Our data support that Na(+)/K(+)-ATPase is functional in maturation-stage ameloblasts.
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Affiliation(s)
- Xin Wen
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
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33
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Abstract
The biological functions of ion channels in tooth development vary according to the nature of their gating, the species of ions passing through those gates, the number of gates, localization of channels, tissue expressing the channel, and interactions between cells and microenvironment. Ion channels feature unique and specific ion flux in ameloblasts, odontoblasts, and other tooth-specific cell lineages. Both enamel and dentin have active chemical systems orchestrating a variety of ion exchanges and demineralization and remineralization processes in a stage-dependent manner. An important role for ion channels is to regulate and maintain the calcium and pH homeostasis that are critical for proper enamel and dentin biomineralization. Specific functions of chloride channels, TRPVs, calcium channels, potassium channels, and solute carrier superfamily members in tooth formation have been gradually clarified in recent years. Mutations in these ion channels or transporters often result in disastrous changes in tooth development. The channelopathies of tooth include altered eruption (CLCN7, KCNJ2, TRPV3), root dysplasia (CLCN7, KCNJ2), amelogenesis imperfecta (KCNJ1, CFTR, AE2, CACNA1C, GJA1), dentin dysplasia (CLCN5), small teeth (CACNA1C, GJA1), tooth agenesis (CLCN7), and other impairments. The mechanisms leading to tooth channelopathies are primarily related to pH regulation, calcium homeostasis, or other alterations of the niche for tooth eruption and development.
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Affiliation(s)
- X Duan
- Department of Oral Biology, Clinic of Oral Rare Diseases and Genetic Diseases, School of Stomatology, The Fourth Military Medical University, Xi'an, 710032, P.R. China
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34
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Kuroda H, Sobhan U, Sato M, Tsumura M, Ichinohe T, Tazaki M, Shibukawa Y. Sodium-calcium exchangers in rat trigeminal ganglion neurons. Mol Pain 2013; 9:22. [PMID: 23628073 PMCID: PMC3646678 DOI: 10.1186/1744-8069-9-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 04/19/2013] [Indexed: 01/10/2023] Open
Abstract
Background Noxious stimulation and nerve injury induce an increase in intracellular Ca2+ concentration ([Ca2+]i) via various receptors or ionic channels. While an increase in [Ca2+]i excites neurons, [Ca2+]i overload elicits cytotoxicity, resulting in cell death. Intracellular Ca2+ is essential for many signal transduction mechanisms, and its level is precisely regulated by the Ca2+ extrusion system in the plasma membrane, which includes the Na+-Ca2+ exchanger (NCX). It has been demonstrated that Ca2+-ATPase is the primary mechanism for removing [Ca2+]i following excitatory activity in trigeminal ganglion (TG) neurons; however, the role of NCXs in this process has yet to be clarified. The goal of this study was to examine the expression/localization of NCXs in TG neurons and to evaluate their functional properties. Results NCX isoforms (NCX1, NCX2, and NCX3) were expressed in primary cultured rat TG neurons. All the NCX isoforms were also expressed in A-, peptidergic C-, and non-peptidergic C-neurons, and located not only in the somata, dendrites, axons and perinuclear region, but also in axons innervating the dental pulp. Reverse NCX activity was clearly observed in TG neurons. The inactivation kinetics of voltage-dependent Na+ channels were prolonged by NCX inhibitors when [Ca2+]i in TG neurons was elevated beyond physiological levels. Conclusions Our results suggest that NCXs in TG neurons play an important role in regulating Ca2+-homeostasis and somatosensory information processing by functionally coupling with voltage-dependent Na+ channels.
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Affiliation(s)
- Hidetaka Kuroda
- Oral Health Science Center hrc8, Tokyo Dental College, Tokyo 261-8502, Japan
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35
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Lacruz RS, Smith CE, Kurtz I, Hubbard MJ, Paine ML. New paradigms on the transport functions of maturation-stage ameloblasts. J Dent Res 2012; 92:122-9. [PMID: 23242231 DOI: 10.1177/0022034512470954] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Fully matured dental enamel is an architecturally and mechanically complex hydroxyapatite-based bioceramic devoid of most of the organic material that was essential in its making. Enamel formation is a staged process principally involving secretory and maturation stages, each associated with major changes in gene expression and cellular function. Cellular activities that define the maturation stage of amelogenesis include ion (e.g., calcium and phosphate) transport and storage, control of intracellular and extracellular pH (e.g., bicarbonate and hydrogen ion movements), and endocytosis. Recent studies on rodent amelogenesis have identified a multitude of gene products that appear to be linked to these cellular activities. This review describes the main cellular activities of these genes during the maturation stage of amelogenesis.
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Affiliation(s)
- R S Lacruz
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA.
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36
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Hu P, Lacruz RS, Smith CE, Smith SM, Kurtz I, Paine ML. Expression of the sodium/calcium/potassium exchanger, NCKX4, in ameloblasts. Cells Tissues Organs 2012; 196:501-9. [PMID: 22677781 DOI: 10.1159/000337493] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2012] [Indexed: 11/19/2022] Open
Abstract
Transcellular calcium transport is an essential activity in mineralized tissue formation, including dental hard tissues. In many organ systems, this activity is regulated by membrane-bound sodium/calcium (Na(+)/Ca(2+)) exchangers, which include the NCX and NCKX [sodium/calcium-potassium (Na(+)/Ca(2+)-K(+)) exchanger] proteins. During enamel maturation, when crystals expand in thickness, Ca(2+) requirements vastly increase but exactly how Ca(2+) traffics through ameloblasts remains uncertain. Previous studies have shown that several NCX proteins are expressed in ameloblasts, although no significant shifts in expression were observed during maturation which pointed to the possible identification of other Ca(2+) membrane transporters. NCKX proteins are encoded by members of the solute carrier gene family, Slc24a, which include 6 different proteins (NCKX1-6). NCKX are bidirectional electrogenic transporters regulating Ca(2+) transport in and out of cells dependent on the transmembrane ion gradient. In this study we show that all NCKX mRNAs are expressed in dental tissues. Real-time PCR indicates that of all the members of the NCKX group, NCKX4 is the most highly expressed gene transcript during the late stages of amelogenesis. In situ hybridization and immunolocalization analyses clearly establish that in the enamel organ, NCKX4 is expressed primarily by ameloblasts during the maturation stage. Further, during the mid-late maturation stages of amelogenesis, the expression of NCKX4 in ameloblasts is most prominent at the apical poles and at the lateral membranes proximal to the apical ends. These data suggest that NCKX4 might be an important regulator of Ca(2+) transport during amelogenesis.
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Affiliation(s)
- Ping Hu
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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Lacruz RS, Smith CE, Bringas P, Chen YB, Smith SM, Snead ML, Kurtz I, Hacia JG, Hubbard MJ, Paine ML. Identification of novel candidate genes involved in mineralization of dental enamel by genome-wide transcript profiling. J Cell Physiol 2012; 227:2264-75. [PMID: 21809343 DOI: 10.1002/jcp.22965] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The gene repertoire regulating vertebrate biomineralization is poorly understood. Dental enamel, the most highly mineralized tissue in mammals, differs from other calcifying systems in that the formative cells (ameloblasts) lack remodeling activity and largely degrade and resorb the initial extracellular matrix. Enamel mineralization requires that ameloblasts undergo a profound functional switch from matrix-secreting to maturational (calcium transport, protein resorption) roles as mineralization progresses. During the maturation stage, extracellular pH decreases markedly, placing high demands on ameloblasts to regulate acidic environments present around the growing hydroxyapatite crystals. To identify the genetic events driving enamel mineralization, we conducted genome-wide transcript profiling of the developing enamel organ from rat incisors and highlight over 300 genes differentially expressed during maturation. Using multiple bioinformatics analyses, we identified groups of maturation-associated genes whose functions are linked to key mineralization processes including pH regulation, calcium handling, and matrix turnover. Subsequent qPCR and Western blot analyses revealed that a number of solute carrier (SLC) gene family members were up-regulated during maturation, including the novel protein Slc24a4 involved in calcium handling as well as other proteins of similar function (Stim1). By providing the first global overview of the cellular machinery required for enamel maturation, this study provide a strong foundation for improving basic understanding of biomineralization and its practical applications in healthcare.
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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, USA.
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Lacruz RS, Smith CE, Moffatt P, Chang EH, Bromage TG, Bringas P, Nanci A, Baniwal SK, Zabner J, Welsh MJ, Kurtz I, Paine ML. Requirements for ion and solute transport, and pH regulation during enamel maturation. J Cell Physiol 2012; 227:1776-85. [PMID: 21732355 DOI: 10.1002/jcp.22911] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Transcellular bicarbonate transport is suspected to be an important pathway used by ameloblasts to regulate extracellular pH and support crystal growth during enamel maturation. Proteins that play a role in amelogenesis include members of the ABC transporters (SLC gene family and CFTR). A number of carbonic anhydrases (CAs) have also been identified. The defined functions of these genes are likely interlinked during enamel mineralization. The purpose of this study is to quantify relative mRNA levels of individual SLC, Cftr, and CAs in enamel cells obtained from secretory and maturation stages on rat incisors. We also present novel data on the enamel phenotypes for two animal models, a mutant porcine (CFTR-ΔF508) and the NBCe1-null mouse. Our data show that two SLCs (AE2 and NBCe1), Cftr, and Car2, Car3, Car6, and Car12 are all significantly up-regulated at the onset of the maturation stage of amelogenesis when compared to the secretory stage. The remaining SLCs and CA gene transcripts showed negligible expression or no significant change in expression from secretory to maturation stages. The enamel of CFTR-ΔF508 adult pigs was hypomineralized and showed abnormal crystal growth. NBCe1-null mice enamel was structurally defective and had a marked decrease in mineral content relative to wild-type. These data demonstrate the importance of many non-matrix proteins to amelogenesis and that the expression levels of multiple genes regulating extracellular pH are modulated during enamel maturation in response to an increased need for pH buffering during hydroxyapatite crystal growth.
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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 90033, USA.
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El-Sayed W, Shore RC, Parry DA, Inglehearn CF, Mighell AJ. Hypomaturation amelogenesis imperfecta due to WDR72 mutations: a novel mutation and ultrastructural analyses of deciduous teeth. Cells Tissues Organs 2010; 194:60-6. [PMID: 21196691 PMCID: PMC3128158 DOI: 10.1159/000322036] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Mutations in WDR72 have been identified in autosomal recessive hypomaturation amelogenesis imperfecta (AI). OBJECTIVE to describe a novel WDR72 mutation and report the ultrastructural enamel phenotype associated with a different WDR72 mutation. METHODS A family segregating autosomal recessive hypomaturation AI was recruited, genomic DNA obtained and WDR72 sequenced. Four deciduous teeth from one individual with a previously published WDR72 mutation, extracted as part of clinical care, were subjected to scanning electron microscopy, energy-dispersive X-ray analysis and transverse microradiography. RESULTS A novel homozygous nonsense mutation, R897X, was identified in WDR72 in a family originating from Pakistan. Ultrastructural analysis of enamel from the deciduous teeth of an AI patient with the WDR72 mutation S783X revealed energy-dispersive X-ray analysis spectra with normal carbon and nitrogen peaks, excluding retention of enamel matrix protein. However, transverse microradiography values were significantly lower for affected teeth when compared to normal teeth, consistent with reduced mineralisation. On scanning electron microscopy the enamel rod form observed was normal, yet with inter-rod enamel more prominent than in controls. This appearance was unaltered following incubation with either α-chymotrypsin or lipase. CONCLUSIONS The novel WDR72 mutation described brings the total reported WDR72 mutations to four. Analyses of deciduous tooth enamel in an individual with a homozygous WDR72 mutation identified changes consistent with a late failure of enamel maturation without retention of matrix proteins. The mechanisms by which intracellular WDR72 influences enamel maturation remain unknown.
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Affiliation(s)
- W El-Sayed
- Leeds Dental Institute, University of Leeds, Leeds, UK
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Tye CE, Sharma R, Smith CE, Bartlett JD. Altered ion-responsive gene expression in Mmp20 null mice. J Dent Res 2010; 89:1421-6. [PMID: 20929715 DOI: 10.1177/0022034510384625] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
During enamel maturation, hydroxyapatite crystallites expand in volume, releasing protons that acidify the developing enamel. This acidity is neutralized by the buffering activity of carbonic anhydrases and ion transporters. Less hydroxyapatite forms in matrix metalloproteinase-20 null (Mmp20(-/-)) mouse incisors, because enamel thickness is reduced by approximately 50%. We therefore asked if ion regulation was altered in Mmp20(-/-) mouse enamel. Staining of wild-type and Mmp20(-/-) incisors with pH indicators demonstrated that wild-type mice had pronounced changes in enamel pH as development progressed. These pH changes were greatly attenuated in Mmp20(-/-) mice. Expression of 4 ion-regulatory genes (Atp2b4, Slc4a2, Car6, Cftr) was significantly decreased in enamel organs from Mmp20(-/-) mice. Notably, expression of secreted carbonic anhydrase (Car6) was reduced to almost undetectable levels in the null enamel organ. In contrast, Odam and Klk4 expression was unaffected. We concluded that a feedback mechanism regulates ion-responsive gene expression during enamel development.
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Affiliation(s)
- C E Tye
- Department of Cytokine Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA
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