Project description:Background: Ameloblast differentiation is the most critical stepwise process in amelogenesis and controlled by a precisely molecules synergistically. To better understand the molecular events defining cell differentiation between preameloblasts and secretory ameloblasts during amelogenesis, a more precise identification of molecules and signaling networks would shed light on the mechanisms governing enamel formation and help lay a foundation for enamel regeneration. Results: Gene expression profiles of human preameloblast and secretory ameloblast cells were obtained using human genome microarrays. From a total of 28,869 analyzed transcripts, 923 differentially expressed genes (DEGs) with FDR<0.01 and Fold-change > 2 were obtained. Among them, more than twice DEGs were found enriched in PAB (n = 647) compared with SAB (n = 276). Notably, 38 genes were identified significantly differentially expressed between PAB and SAB (Fold Change > 8). Comparison of transcriptional profiles of PAB and SAB together with KEGG pathway analysis revealed genes enrichment in PAB were chiefly involved in cell cycle control, DNA damage repair and apoptosis, while genes related to cell adhesion and extracellular matrix had elevated expression level in SAB. Two co-expression modules were further identified significantly associated with the ameloblast differentiation process by weighted gene co-expression network analysis (WGCNA).These gene networks seem to contribute to cell adhesion, tissue development, cell signaling and division. Furthermore, the co-expression associations of RunX2 and BMP8A were also observed in these modules. Conclusions: In this study, we uncovered that the differentiation from PAB to SAB may rely on a highly regulated network of interactions between conserved signal transduction pathways, including members of BMP/TGF-β, Notch, MAPK pathways to coordinate all aspects of ameloblast in intracellular processes and their social contexts. Specifically, expression of genes associated with cell cycle control, DNA damage repair, and apoptosis pathways regulates pre-ameloblast maturation during tooth development. And the SAB cells are regulated by several signaling pathways controlling enamel matrix proteins secretion and cell adhesion, which are critical for enamel formation and cell-cell interactions. Apart from showing the transcriptional patterns of PAB and SAB, the application of bioinformatic analysis also explored the potential key genes and gene-associations in ameloblast differentiation. These findings will aid in the design of new strategies to promote ameloblast functional differentiation in the regeneration and tissue engineering of teeth. Human tooth buds (18-22 weeks) were obtained from fetal cadaver tissue within 3 hours after legal abortion. Teeth were dissected from the mandibles under a laminar flow hood, embedded in OCT compound, and cryosectioned at 10-μm thickness. These sections were used for laser capture microdissection (LCM). In total of 3 pre-ameloblasts and 3 secretory ameloblasts pooled samples were used for RNA extraction and hybridization on Affymetrix microarray.
Project description:The goal of the study was to characterize the whole genome transcriptome profiles of human ameloblasts and odontoblasts, evaluate molecular pathways and advance our knowledge of the human tooth development. We found that during primary tooth formation, odontoblasts expressed 14,802 genes, presecretory ameloblasts 15,179 genes and secretory ameloblasts 14,526 genes. Four human fetuses were obtained at ages 15-20 weeks gestation, immediately placed on ice and the tooth buds dissected from the jaws, placed in RNAlater and refrigerated at 4C for 1-4 weeks to allow decalcification by EDTA. The tissue was then frozen and stored at -80C. The tissue was sectioned at -35C at a thickness of 7 microns. These sections were used for laser capture microdissection (LCM) to isolate the human odontoblasts and ameloblasts in different stages of enamel formation, using static image settings. In total, 4 odontoblast, 4 pre-secretory ameloblast and 4 secretory ameloblast pooled samples were used for RNA extraction and microarray analysis.
Project description:In order to identify the genes that are specific to the ameloblast phenotype, we collected epithelial cells differentiated from HESCs (ES-EC), human fetal oral epithelia cells (OE), and presecretory ameloblasts (PAB) and SAB, and conducted the microarray to compare the overall transcription patterns of these four cell types. Stage specific ameloblasts did exhibit distinctive gene expression patterns as comapred to non-dental epithelia cells ES-EC and OE. There were 908 genes in PAB and 1203 genes in SAB that were either down-regulated or upregulated more than 2.0-fold as comapred to the non-dental epthelial cells ( average of ES-EC and OE)
Project description:We compared the overall gene expression pattern between secretory ameloblasts and maturation ameloblasts, and found out there were 244 genes differentially exppressed in the maturation ameloblasts as compared to secretory ameloblasts. Upon treatment, the genes coregulated with MMP-20 were downregulated in maturation ameloblasts, though the difference was not significant. Stage specific secretory ameloblasts (SAB) and maturation ameloblasts (MAB) were laser microdissected from mandibular incisors of control and 50 ppm F treated mice.
Project description:The goal of the study was to characterize the whole genome transcriptome profiles of human ameloblasts and odontoblasts, evaluate molecular pathways and advance our knowledge of the human tooth development. We found that during primary tooth formation, odontoblasts expressed 14,802 genes, presecretory ameloblasts 15,179 genes and secretory ameloblasts 14,526 genes.
Project description:We compared the overall gene expression pattern between secretory ameloblasts and maturation ameloblasts, and found out there were 244 genes differentially exppressed in the maturation ameloblasts as compared to secretory ameloblasts. Upon treatment, the genes coregulated with MMP-20 were downregulated in maturation ameloblasts, though the difference was not significant.
Project description:Tooth enamel secreted by ameloblasts is the hardest material in the human body, acting as a shield protecting the teeth. However, enamel is gradually damaged or partially lost in over 90% of adults and cannot be regenerated due to a lack of ameloblasts in erupted teeth. Here we use sci-RNA-seq to establish a spatiotemporal single cell atlas for the developing human tooth and identify regulatory mechanisms controlling the differentiation process of human ameloblasts. We reveal key signaling pathways involved between the support cells and ameloblasts during fetal development and recapitulate those findings in a novel human ameloblast in vitro differentiation from iPSCs. We furthermore develop a mineralizing enamel organ-like 3D organoid system. These studies pave the way for future regenerative dentistry and therapies toward genetic diseases affecting enamel formation.
Project description:Throughout the various stages of tooth development, reciprocal epithelial-mesenchymal interactions are the driving force, for instance crucially involved in the differentiation of mature enamel-forming ameloblasts and dentin-producing odontoblasts. Here we established mouse tooth ‘assembloids’, comprised of tooth organoid-derived dental epithelial cells (from mouse molars and incisors) cultured together with molar dental pulp stem cells (DPSCs), to mimic these developmental interactions. Assembloids from both tooth types were grown both in basal- and differentiation-inducing conditions. Single cell transcriptomics analysis was applied to in detail characterize and validate the newly developed mouse tooth assembloid model and evaluate the induced differentiation processes.
Project description:Coordinated mineralization of soft tissue is central to organismal form and function, while dysregulated mineralization underlies several human pathologies. Oral epithelial derived ameloblasts are polarized, secretory cells responsible for generating enamel, the most mineralized substance in the human body. Defects in ameloblast development result in enamel anomalies, including amelogenesis imperfecta. Identifying proteins critical in ameloblast development can provide insight into specific pathologies associated with enamel related disorders or more broadly, mechanisms of mineralization. Previous studies identified a role for MEMO1 in bone mineralization; however, whether MEMO1 functions in the generation of additional mineralized structures remains unknown. Here, we identify a critical role for MEMO1 in enamel mineralization. First, we identified that Memo1 is expressed in ameloblasts and that conditional deletion of Memo1 from ameloblasts results in enamel defects, characterized by a decline in mineral density and tooth integrity. Molecular profiling of ameloblasts and their progenitors in Memo1 oral epithelial mutants revealed a disruption to cytoskeletal associated genes and a reduction in late stage ameloblast markers, relative to controls. Histology revealed that the molecular defects correlated with a disruption of the apical Tome’s process and the basolateral interacting, papillary layer, in Memo1 mutant ameloblasts. Finally, deletion of Memo1 from an oral epithelial ameloblast cell line, followed by cellular and molecular analyses, revealed altered cytoskeletal networks, relative to control cells. Collectively, our findings integrate MEMO1 into an emerging network of molecules important for ameloblast development and provide both in vivo and in vitro systems to further interrogate the relationship of cytoskeletal and amelogenesis-related defects.
Project description:We used RNA-seq to identify differentially expressed genes across ameloblast stages in rats. We found expression patterns of enamel matrix proteins, ion channels and transporters, and endocytosis regulators such as clathrin to match those found in previous experimental studies on ameloblasts. We hypothesized that ameloblasts change their endocytotic pathways as they progress from stage and stage, and we sought to identify novel patterns in expression of genes at the endocytosis/cytoskeleton interface. We found that maturation ameloblasts preferentially express synaptojanin 1 and intersectin 2 and secretory ameloblasts preferentially express Numb protein and amphiphysin. We also uncovered differential alternative splicing of ECI genes across ameloblast populations. In pointing to endocytotic genes hitherto unexplored in ameloblasts that also regulate cell morphology, this bioinformatics study suggests a mechanism by which cervical loop, secretory, and maturation ameloblasts switch modes of endocytosis in order to express genes that better suit the distinct morphology of each cell stage.