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The International Journal of... Feb 1995The formation and mineralization of enamel is controlled by epithelial cells of the enamel organ which undergo marked, and in some cases repetitive, alterations in... (Review)
Review
The formation and mineralization of enamel is controlled by epithelial cells of the enamel organ which undergo marked, and in some cases repetitive, alterations in cellular morphology as part of the developmental process. The most dramatic changes are seen in ameloblasts which reverse their secretory polarity during differentiation to allow for extracellular release of large amounts of proteins from plasma membrane surfaces that were originally the embryonic bases of the cells. Secreted enamel proteins at first do not accumulate in a layer but, in part, percolate into the developing predentin and subjacent odontoblast layer. Appositional growth of an enamel layer begins with mineralization of the dentin, and ameloblasts develop a complicated functional apex (Tome's processes) to direct release of matrix proteins, and perhaps proteinases, at interrod and rod growth sites. Once the full thickness of enamel is produced, some ameloblasts degenerate, and the surviving cells shorten in height and spread out at the enamel surface. They reform a basal lamina to cover the immature enamel, and continue producing small amounts of enamel proteins that pass through the basal lamina into the enamel. Ameloblasts also undergo cycles of modulation where apical invaginations enriched in Ca-ATPases and other enzymes are formed and shed on a repetitive basis (ruffle-ended/smooth-ended transitions). As this happens, apatetic crystals seeded earlier expand in volume by gradual layering of new mineral at the surfaces of the preformed crystals. Ameloblasts stop modulating when the crystals almost fill existing volume formerly occupied by protein and water.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Ameloblasts; Amelogenesis; Animals; Cell Differentiation; Dental Enamel; Humans; Male; Rats; Rats, Sprague-Dawley
PubMed: 7626402
DOI: No ID Found -
The International Journal of... Feb 1995This paper reviews the primary structure, characteristics and possible function of tuftelin/enamelin protein. It describes the distribution of tuftelin in the ameloblast... (Review)
Review
This paper reviews the primary structure, characteristics and possible function of tuftelin/enamelin protein. It describes the distribution of tuftelin in the ameloblast cell and in the extracellular enamel matrix, employing high resolution protein-A gold immunocytochemistry. The chromosomal localization of the human tuftelin gene and its possible involvement in autosomally linked Amelogenesis Imperfecta, the most common hereditary disease of enamel, is also discussed.
Topics: Ameloblasts; Amelogenesis Imperfecta; Animals; Chromosome Mapping; Chromosomes, Human, Pair 1; Dental Enamel Proteins; Extracellular Matrix; Humans
PubMed: 7626400
DOI: No ID Found -
Brazilian Oral Research 2020Induced pluripotent stem (iPS) cells could be induced into ameloblast-like cells by ameloblasts serum-free conditioned medium (ASF-CM), and bone morphogenetic proteins...
Induced pluripotent stem (iPS) cells could be induced into ameloblast-like cells by ameloblasts serum-free conditioned medium (ASF-CM), and bone morphogenetic proteins (BMPs) might be essential during the regulation of this process. The present study investigates the signal transduction that regulates the ameloblastic differentiation of iPS cells induced by ASF-CM. Mouse iPS cells were characterized and then cultured for 14 days in epithelial cell medium (control) or ASF-CM. Bone morphogenetic protein receptor II (BMPR-II) siRNA, inhibitor of Smad1/5 phosphorylation activated by activin receptor-like kinase (ALK) receptors, and inhibitors of mitogen-activated protein kinases (MAPKs) phosphorylation were used to treat the iPS cells in combination with ASF-CM. Real-time PCR, western blotting, and immunofluorescent staining were used to evaluate the expressions of ameloblast markers ameloblastin, enamelin, and cytokeratin-14. BMPR-II gene and protein levels increased markedly in ASF-CM-treated iPS cells compared with the controls, while the mRNA levels of Bmpr-Ia and Bmpr-Ib were similar between the ASF-CM and control groups. ASF-CM stimulation significantly increased the gene and protein expression of ameloblastin, enamelin and cytokeratin-14, and phosphorylated SMAD1/5, p38 MAPK, and ERK1/2 MAPK compared with the controls. Knockdown of BMPR-II and inhibition of Smad1/5 phosphorylation both could significantly reverse the increased expression of ameloblastin, enamelin, and cytokeratin-14 induced by ASF-CM, while neither inhibition of p38 nor ERK1/2 phosphorylation had significant reversing effects. We conclude that smad1/5 signaling transduction, activated by ALK receptors, regulates the ameloblastic differentiation of iPS cells induced by ameloblast-conditioned medium.
Topics: Activin Receptors; Ameloblasts; Blotting, Western; Bone Morphogenetic Protein Receptors, Type II; Cell Differentiation; Cells, Cultured; Culture Media, Serum-Free; Fluorescent Antibody Technique; Gene Expression; Induced Pluripotent Stem Cells; MAP Kinase Signaling System; Phosphorylation; RNA Interference; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Smad1 Protein; Time Factors; p38 Mitogen-Activated Protein Kinases
PubMed: 32022225
DOI: 10.1590/1807-3107bor-2020.vol34.0006 -
PloS One 2011To explore gene therapy strategies for amelogenesis imperfecta (AI), a human ameloblast-like cell population was established from third molars of an AI-affected patient....
To explore gene therapy strategies for amelogenesis imperfecta (AI), a human ameloblast-like cell population was established from third molars of an AI-affected patient. These cells were characterized by expression of cytokeratin 14, major enamel proteins and alkaline phosphatase staining. Suboptimal transduction of the ameloblast-like cells by an adenovirus type 5 (Ad5) vector was consistent with lower levels of the coxsackie-and-adenovirus receptor (CAR) on those cells relative to CAR-positive A549 cells. To overcome CAR -deficiency, we evaluated capsid-modified Ad5 vectors with various genetic capsid modifications including "pK7" and/or "RGD" motif-containing short peptides incorporated in the capsid protein fiber as well as fiber chimera with the Ad serotype 3 (Ad3) fiber "knob" domain. All fiber modifications provided an augmented transduction of AI-ameloblasts, revealed following vector dose normalization in A549 cells with a superior effect (up to 404-fold) of pK7/RGD double modification. This robust infectivity enhancement occurred through vector binding to both α(v)β3/α(v)β5 integrins and heparan sulfate proteoglycans (HSPGs) highly expressed by AI-ameloblasts as revealed by gene transfer blocking experiments. This work thus not only pioneers establishment of human AI ameloblast-like cell population as a model for in vitro studies but also reveals an optimal infectivity-enhancement strategy for a potential Ad5 vector-mediated gene therapy for AI.
Topics: Adenoviridae; Adolescent; Ameloblasts; Amelogenesis Imperfecta; Capsid; Cell Line, Tumor; Coxsackie and Adenovirus Receptor-Like Membrane Protein; Genetic Vectors; Humans; Receptors, Virus; Transduction, Genetic; Viral Tropism
PubMed: 22003382
DOI: 10.1371/journal.pone.0024281 -
STAR Protocols Jun 2024Adult humans cannot regenerate the enamel-forming cell type, ameloblasts. Hence, human induced pluripotent stem cell (hiPSC)-derived ameloblasts are valuable for...
Adult humans cannot regenerate the enamel-forming cell type, ameloblasts. Hence, human induced pluripotent stem cell (hiPSC)-derived ameloblasts are valuable for investigating tooth development and regeneration. Here, we present a protocol for generating three-dimensional induced early ameloblasts (ieAMs) utilizing serum-free media and growth factors. We describe steps for directing hiPSCs toward oral epithelium and then toward ameloblast fate. These cells can form suspended early ameloblast organoids. This approach is critical for understanding, treating, and promoting regeneration in diseases like amelogenesis imperfecta. For complete details on the use and execution of this protocol, please refer to Alghadeer et al..
Topics: Ameloblasts; Humans; Culture Media, Serum-Free; Induced Pluripotent Stem Cells; Cell Culture Techniques; Intercellular Signaling Peptides and Proteins; Cell Differentiation; Cells, Cultured
PubMed: 38824640
DOI: 10.1016/j.xpro.2024.103100 -
International Journal of Molecular... Feb 2021Amelogenesis imperfecta is a congenital form of enamel hypoplasia. Although a number of genetic mutations have been reported in humans, the regulatory network of these...
Amelogenesis imperfecta is a congenital form of enamel hypoplasia. Although a number of genetic mutations have been reported in humans, the regulatory network of these genes remains mostly unclear. To identify signatures of biological pathways in amelogenesis imperfecta, we conducted bioinformatic analyses on genes associated with the condition in humans. Through an extensive search of the main biomedical databases, we found 56 genes in which mutations and/or association/linkage were reported in individuals with amelogenesis imperfecta. These candidate genes were further grouped by function, pathway, protein-protein interaction, and tissue-specific expression patterns using various bioinformatic tools. The bioinformatic analyses highlighted a group of genes essential for extracellular matrix formation. Furthermore, advanced bioinformatic analyses for microRNAs (miRNAs), which are short non-coding RNAs that suppress target genes at the post-transcriptional level, predicted 37 candidates that may be involved in amelogenesis imperfecta. To validate the miRNA-gene regulation association, we analyzed the target gene expression of the top seven candidate miRNAs: miR-3195, miR-382-5p, miR-1306-5p, miR-4683, miR-6716-3p, miR-3914, and miR-3935. Among them, miR-1306-5p, miR-3195, and miR-3914 were confirmed to regulate ameloblast differentiation through the regulation of genes associated with amelogenesis imperfecta in AM-1 cells, a human ameloblastoma cell line. Taken together, our study suggests a potential role for miRNAs in amelogenesis imperfecta.
Topics: Ameloblasts; Amelogenesis Imperfecta; Cell Differentiation; Cell Line; Computational Biology; Humans; MicroRNAs; Protein Interaction Maps; Reproducibility of Results
PubMed: 33672174
DOI: 10.3390/ijms22042202 -
Journal of Bone and Mineral Research :... Jun 2005The recognized structural proteins of the enamel matrix are amelogenin, ameloblastin, and enamelin. While a large volume of data exists showing that amelogenin...
UNLABELLED
The recognized structural proteins of the enamel matrix are amelogenin, ameloblastin, and enamelin. While a large volume of data exists showing that amelogenin self-assembles into multimeric units referred to as nanospheres, other reports of enamel matrix protein-protein interactions are scant. We believe that each of these enamel matrix proteins must interact with other organic components of ameloblasts and the enamel matrix. Likely protein partners would include integral membrane proteins and additional secreted proteins.
INTRODUCTION
The purpose of this study was to identify and catalog additional proteins that play a significant role in enamel formation.
MATERIALS AND METHODS
We used the yeast two-hybrid assay to identify protein partners for amelogenin, ameloblastin, and enamelin. Once identified, RT-PCR was used to assess gene transcription of these newly identified and potential "enamel" proteins in ameloblast-like LS8 cells.
RESULTS
In the context of this yeast assay, we identified a number of secreted proteins and integral membrane proteins that interact with amelogenin, ameloblastin, and enamelin. Additionally, proteins whose functions range from the inhibition of soft tissue mineralization, calcium ion transport, and phosphorylation events have been identified as protein partners to these enamel matrix proteins. For each protein identified using this screening strategy, future studies are planned to confirm this physiological relationship to biomineralization in vivo.
CONCLUSION
Identifying integral membrane proteins of the secretory surface of ameloblast cells (Tomes' processes) and additional enamel matrix proteins, based on their abilities to interact with the most abundant enamel matrix proteins, will better define the molecular mechanisms of enamel formation at its most rudimentary level.
Topics: Ameloblasts; Amelogenin; Animals; Antigens, CD; Biglycan; Blood Proteins; Calnexin; Cell Membrane; DNA, Complementary; Dental Enamel; Dental Enamel Proteins; Dentin; Extracellular Matrix Proteins; Mice; Models, Biological; Open Reading Frames; Phosphorylation; Platelet Membrane Glycoproteins; Protein Binding; Proteoglycans; RNA, Messenger; Reverse Transcriptase Polymerase Chain Reaction; Tetraspanin 30; Time Factors; Transcription, Genetic; Two-Hybrid System Techniques; alpha-2-HS-Glycoprotein; alpha-Fetoproteins
PubMed: 15883644
DOI: 10.1359/JBMR.050111 -
PloS One 2014Mutations in the human enamelin gene cause autosomal dominant hypoplastic amelogenesis imperfecta in which the affected enamel is thin or absent. Study of enamelin...
Mutations in the human enamelin gene cause autosomal dominant hypoplastic amelogenesis imperfecta in which the affected enamel is thin or absent. Study of enamelin knockout NLS-lacZ knockin mice revealed that mineralization along the distal membrane of ameloblast is deficient, resulting in no true enamel formation. To determine the function of enamelin during enamel formation, we characterized the developing teeth of the Enam-/- mice, generated amelogenin-driven enamelin transgenic mouse models, and then introduced enamelin transgenes into the Enam-/- mice to rescue enamel defects. Mice at specific stages of development were subjected to morphologic and structural analysis using β-galactosidase staining, immunohistochemistry, and transmission and scanning electron microscopy. Enamelin expression was ameloblast-specific. In the absence of enamelin, ameloblasts pathology became evident at the onset of the secretory stage. Although the aggregated ameloblasts generated matrix-containing amelogenin, they were not able to create a well-defined enamel space or produce normal enamel crystals. When enamelin is present at half of the normal quantity, enamel was thinner with enamel rods not as tightly arranged as in wild type suggesting that a specific quantity of enamelin is critical for normal enamel formation. Enamelin dosage effect was further demonstrated in transgenic mouse lines over expressing enamelin. Introducing enamelin transgene at various expression levels into the Enam-/- background did not fully recover enamel formation while a medium expresser in the Enam+/- background did. Too much or too little enamelin abolishes the production of enamel crystals and prism structure. Enamelin is essential for ameloblast integrity and enamel formation.
Topics: Ameloblasts; Amelogenin; Animals; Animals, Newborn; Dental Enamel; Dental Enamel Proteins; Dentin; Immunohistochemistry; Mice, Knockout; Mice, Transgenic; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Molar; Staining and Labeling; beta-Galactosidase
PubMed: 24603688
DOI: 10.1371/journal.pone.0089303 -
Journal of Dental Research Oct 2009Intake of excess amounts of fluoride during tooth development cause enamel fluorosis, a developmental disturbance that makes enamel more porous. In mild fluorosis, there... (Review)
Review
Intake of excess amounts of fluoride during tooth development cause enamel fluorosis, a developmental disturbance that makes enamel more porous. In mild fluorosis, there are white opaque striations across the enamel surface, whereas in more severe cases, the porous regions increase in size, with enamel pitting, and secondary discoloration of the enamel surface. The effects of fluoride on enamel formation suggest that fluoride affects the enamel-forming cells, the ameloblasts. Studies investigating the effects of fluoride on ameloblasts and the mechanisms of fluorosis are based on in vitro cultures as well as animal models. The use of these model systems requires a biologically relevant fluoride dose, and must be carefully interpreted in relation to human tooth formation. Based on these studies, we propose that fluoride can directly affect the ameloblasts, particularly at high fluoride levels, while at lower fluoride levels, the ameloblasts may respond to local effects of fluoride on the mineralizing matrix. A new working model is presented, focused on the assumption that fluoride increases the rate of mineral formation, resulting in a greater release of protons into the forming enamel matrix.
Topics: Ameloblasts; Amelogenesis; Animals; Cariostatic Agents; Cells, Cultured; Dental Enamel; Disease Models, Animal; Fluorides; Fluorosis, Dental; Humans; Models, Biological; Odontogenesis; Tooth Calcification
PubMed: 19783795
DOI: 10.1177/0022034509343280 -
Data in Brief Jun 2022This article contains data related to the research article in this issue titled ameloblastin promotes polarization of ameloblast cell lines in a 3D cell culture system...
This article contains data related to the research article in this issue titled ameloblastin promotes polarization of ameloblast cell lines in a 3D cell culture system (Visakan et al., 2022). In the process of amelogenesis, the organic matrix components are pivotal to the establishment of ameloblast-matrix adhesion. Here we employ immortalized ameloblast cell lines and analyse their morphological changes in 3D cell culture when cultured in the presence of recombinant enamel matrix proteins- ameloblastin and amelogenin compared with controls. The recombinant proteins that were purified using high-performance liquid chromatography (HPLC) were characterized using SDS-gel electrophoresis. A 3D-on-top culture technique was employed, and the cells were analysed 24 and 72 h post inoculation using fluorescent and confocal microscopy for qualitative and quantitative changes. Aspect ratio of cells was measured and used as the parameter to compare between test proteins and controls. Repeated measurements of aspect ratio were recorded to analyse for statistical significance. Additionally, three distinct gel substrates were studied to examine the effect of composition and stiffness of the substrate on cell behaviour. The cells in the 3D culture were fixed and labelled using antibodies to junctional complex, polarity and tight junctional proteins following protocols for whole culture fixation. Co-localization between membrane and specific antibody labels were examined under confocal microscopy.
PubMed: 35586397
DOI: 10.1016/j.dib.2022.108233