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.
Project description:Bcl9 and Bcl9l (Bcl9l) are commonly thought as beta-catenin-dependent Wnt signaling transcriptional activators. We find however that, in the enamel-producin ameloblasts cells, Bcl9/9l are localiyed in the cytoplasm toward to apical secretory membrane. We performed pull down followed by mass spectrometry analysis to discover the molecular partners of Bcl9 that could explain this cytoplasmic localyzation.
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:Incisor enamel organ epithelial cells were isolated and enzymatically processed from postnatal day 4 mice transgenic for Amelx-promoter driven tdTomato. Single cell suspensions were subjected to fluorescence-activated cell sorting (FACS) to isolate tdTomato positive ameloblasts. tdTomato-positive cells were isolated from enamel organ epithelial from the incisors of three mouse lines, which were Mmp20+/+ -AT4 (WT), Mmp20-/--AT4 (KO), Mmp20+/+ Tg-AT4 (Tg, overexpress MMP20). We used Fukuoka Dental College mouse ameloblast PCR array panel to quantitate gene expression of genes associated with enamel formation, cell migration and cell adhesion from ameloblasts.
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: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:Enamel, the hardest material in the human body, is required to protect the living organ, tooth. However, over 90% of adults have lost or damaged enamel and cannot regenerate the protective structure due to lack of enamel producing cells, ameloblasts. iPSC derived secretory Ameloblasts (isAM) have promise in future regenerative dentistry. Today it is not known why iAM maturation requires intimate contact with the dentin producing cell type, odontoblast. Here we reveal that one of the critical signaling ligands emanating from odontoblasts for ameloblast maturation is Delta, the ligand for Notch receptor. We showed that our designed, soluble Notch agonist can induce iAM organoid maturation in an unprecedented manner, without interactions with odontoblast layer. Notably, soluble Notch agonist induces the iAM maturation to a novel, WDR72 positive mature secretory AM stage (ismAM) in our ameloblast organoid model. When transplanted under the kidney capsule of NOD-SCID mice, these ismAM organoids generated enamel-like calcified material, as confirmed by microCT analysis, marking the first demonstration that Notch-activated iAM organoids can form such tissue in vivo. This novel maturation procedure enabled us to analyze the specific requirements of DLX3 function in ameloblasts, independent of its known function in odontoblasts. We now show that DLX3, the gene associated with Amelogenesis Imperfecta, is required on a cell-autonomous manner in human ameloblasts for the expression of Enamelin, MMP20 and WDR72, a role not previously demonstrated in mouse models.
Project description:Ameloblast differentiation is the most critical stepwise process in amelogenesis, and it is controlled by precise molecular events. To better understand the mechanism controlling pre-ameloblasts (PABs) differentiation into secretory ameloblasts (SABs), a more precise identification of molecules and signaling networks will elucidate the mechanisms governing enamel formation and lay a foundation for enamel regeneration. We analyzed transcriptional profiles of human PABs and SABs. From a total of 28,869 analyzed transcripts, we identified 923 differentially expressed genes (DEGs) with p < 0.05 and Fold-change > 2. Among the DEGs, 647 genes showed elevated expression in PABs compared to SABs. Notably, 38 DEGs displayed more than eight-fold changes. Comparative analysis revealed that highly expressed genes in PABs were involved in cell cycle control, DNA damage repair and apoptosis, while highly expressed genes in SABs were related to cell adhesion and extracellular matrix. Moreover, coexpression network analysis uncovered two highly conserved sub-networks contributing to the differentiation, containing transcription regulators (RUNX2, ETV1 and ETV5), solute carrier family members (SLC15A1 and SLC7A11), enamel matrix protein (MMP20), and a polymodal excitatory ion channel (TRPA1). By combining comparative analysis and coexpression networks, this study provides novel biomarkers and research targets for ameloblast differentiation and the potential for their application in enamel regeneration.