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Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development.

ABSTRACT: Runt-related transcription factor 2 (Runx2) is involved in the early stage of tooth development. However, only few studies have reported the role of Runx2 in enamel development, which may be attributed to that Runx2 full knockout mice cannot survive after birth. In the present study, we successfully established a Runx2-deficient mouse model using a conditional knockout (cKO) method. We observed a significant reduction in the degree of mineralization and the decreased size of enamel rods in cKO mice. Histological analysis showed the retained enamel proteins in enamel layer at maturation stage in cKO molars. Further analysis by qRT-PCR revealed that the expressions of genes encoding enamel structure proteins, such as amelogenin (AMELX), ameloblastin (AMBN) and enamelin (ENAM), were increased in cKO enamel organs. On the other hand, the expression of kallikrein-related peptidase-4 (KLK4) at the mRNA and protein levels was dramatically decreased from late secretory stage to maturation stage in cKO enamel organs, while the expression of matrix metalloproteinase-20 (MMP-20) was not significantly altered. Finally, immunohistochemistry indicated that the uptake of amelogenins by ameloblasts was significantly decreased in cKO mice. Taken together, Runx2 played critical roles in controlling enamel maturation by increasing synthesis of KLK4 and decreasing synthesis of AMELX, AMBN and ENAM.

SUBMITTER: Chu Q

PROVIDER: S-EPMC6018461 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development.

Chu Qing Q Gao Yan Y Gao Xianhua X Dong Zhiheng Z Song Wenying W Xu Zhenzhen Z Xiang Lili L Wang Yumin Y Zhang Li L Li Mingyu M Gao Yuguang Y

Scientific reports 20180625 1

Runt-related transcription factor 2 (Runx2) is involved in the early stage of tooth development. However, only few studies have reported the role of Runx2 in enamel development, which may be attributed to that Runx2 full knockout mice cannot survive after birth. In the present study, we successfully established a Runx2-deficient mouse model using a conditional knockout (cKO) method. We observed a significant reduction in the degree of mineralization and the decreased size of enamel rods in cKO m ...[more]

PMID: 29941908

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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.

Dataset Information

Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development.

Publications

Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development.

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