Dataset Information

Calcium Sets the Clock in Ameloblasts.

ABSTRACT:

Background

Stromal interaction molecule 1 (STIM1) is one of the main components of the store operated Ca²⁺ entry (SOCE) signaling pathway. Individuals with mutated STIM1 present severely hypomineralized enamel characterized as amelogenesis imperfecta (AI) but the downstream molecular mechanisms involved remain unclear. Circadian clock signaling plays a key role in regulating the enamel thickness and mineralization, but the effects of STIM1-mediated AI on circadian clock are unknown.

Objectives

The aim of this study is to examine the potential links between SOCE and the circadian clock during amelogenesis.

Methods

We have generated mice with ameloblast-specific deletion of Stim1 (Stim1 ^fl/fl/Amelx-iCre^+/+, Stim1 cKO) and analyzed circadian gene expression profile in Stim1 cKO compared to control (Stim1 ^fl/fl/Amelx-iCre^-/-) using ameloblast micro-dissection and RNA micro-array of 84 circadian genes. Expression level changes were validated by qRT-PCR and immunohistochemistry.

Results

Stim1 deletion has resulted in significant upregulation of the core circadian activator gene Brain and Muscle Aryl Hydrocarbon Receptor Nuclear Translocation 1 (Bmal1) and downregulation of the circadian inhibitor Period 2 (Per2). Our analyses also revealed that SOCE disruption results in dysregulation of two additional circadian regulators; p38α mitogen-activated protein kinase (MAPK14) and transforming growth factor-beta1 (TGF-β1). Both MAPK14 and TGF-β1 pathways are known to play major roles in enamel secretion and their dysregulation has been previously implicated in the development of AI phenotype.

Conclusion

These data indicate that disruption of SOCE significantly affects the ameloblasts molecular circadian clock, suggesting that alteration of the circadian clock may be partly involved in the development of STIM1-mediated AI.

SUBMITTER: Said R

PROVIDER: S-EPMC7411184 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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.