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MEMO1 is required for ameloblast maturation and functional enamel formation

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE235869 | GEO | 2023/08/03

REPOSITORIES: GEO

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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.

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MEMO1 is required for ameloblast maturation and functional enamel formation

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