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Dpysl4 is involved in tooth germ morphogenesis through growth regulation, polarization and differentiation of dental epithelial cells.

ABSTRACT: Dihydropyrimidinase-related protein 4 (Dpysl4) is a known regulator of hippocampal neuron development. Here, we report that Dpysl4 is involved in growth regulation, polarization and differentiation of dental epithelial cells during tooth germ morphogenesis. A reduction in Dpysl4 gene expression in the tooth germ produced a loss of ameloblasts, resulting in the decrease of synthesis and secretion of enamel. The inhibition of Dpysl4 gene expression led to promotion of cell proliferation of inner enamel epithelial cells and inhibition of the differentiation of these cells into pre-ameloblasts, which was confirmed by analyzing cell polarization, columnar cell structure formation and the expression of ameloblast marker genes. By contrast, overexpression of Dpysl4 in dental epithelial cells induces inhibition of growth and increases the expression of the inner enamel epithelial cell marker gene, Msx2. These findings suggest that Dpysl4 plays essential roles in tooth germ morphogenesis through the regulation of dental epithelial cell proliferation, cell polarization and differentiation.

SUBMITTER: Yasukawa M

PROVIDER: S-EPMC3638293 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Dpysl4 is involved in tooth germ morphogenesis through growth regulation, polarization and differentiation of dental epithelial cells.

Yasukawa Masato M Ishida Kentaro K Yuge Yohei Y Hanaoka Mai M Minami Yoko Y Ogawa Miho M Sasaki Takashi T Saito Masahiro M Tsuji Takashi T

International journal of biological sciences 20130426 4

Dihydropyrimidinase-related protein 4 (Dpysl4) is a known regulator of hippocampal neuron development. Here, we report that Dpysl4 is involved in growth regulation, polarization and differentiation of dental epithelial cells during tooth germ morphogenesis. A reduction in Dpysl4 gene expression in the tooth germ produced a loss of ameloblasts, resulting in the decrease of synthesis and secretion of enamel. The inhibition of Dpysl4 gene expression led to promotion of cell proliferation of inner e ...[more]

PMID: 23630450

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Project description:Murine tooth germ development proceeds in continuous and sequential steps with reciprocal interactions between the odontogenic epithelium and the adjacent mesenchyme, and several growth factor signaling and their activation are required for tooth germ development. The expression of ADP-ribosylation factor (Arf)-like 4c (Arl4c) has been shown to induce cell proliferation, thereby involving in epithelial morphogenesis and tumorigenesis. However, other functions of Arl4c except for cellular growth are largely unknown. Although we recently demonstrated the involvement of the upregulated expression of Arl4c in cell proliferation of ameloblastoma, which has the same origin as odontogenic epithelium, its effect on tooth germ development remains unclear. Herein, single-cell RNA sequencing (scRNA-seq) analysis revealed that the expression of Arl4c, among 17 members of the Arf-family members, was specifically detected in odontogenic epithelial cells, such as stratum intermedium, stella reticulum and outer enamel epithelium, of postnatal day 1 (P1) mouse molar. In addition, scRNA-seq analysis showed higher expression of Arl4c in non-ameloblast and inner enamel epithelium, which include immature cells. In the mouse tooth germ rudiments culture, treatment with SecinH3 (an inhibitor of ARNO/Arf6 pathway) reduced the size, width and cusp height and the thickness of eosinophilic layer, which would involve the synthesis of dentin and enamel matrix organization. In addition, loss-of-function experiments using siRNAs and shRNA revealed that Arl4c expression was involved in cell proliferation and osteoblastic cytodifferentiation in odontogenic epithelial cells. Finally, RNA-seq analysis with gene set enrichment analyses (GSEA) and Gene Ontology (GO) analysis showed that osteoblastic differentiation-related gene set and/or GO terms were downregulated in shArl4c expressing odontogenic epithelial cells. These results suggest that the Arl4c-ARNO/Arf6 pathway axis contributes to tooth germ development through osteoblastic differentiation.

Project description:Tooth morphogenesis involves dynamic changes in shape and size as it proceeds through the bud, cap, and bell stages. This process requires exact regulation of cell proliferation and differentiation. Smad7, a general antagonist against transforming growth factor-? (TGF-?) signaling, is necessary for maintaining homeostasis and proper functionality in many organs. While TGF-? signaling is widely involved in tooth morphogenesis, the precise role of Smad7 in tooth development remains unknown. In this study, we showed that Smad7 is expressed in the developing mouse molars with a high level in the dental epithelium but a moderate to weak level in the dental mesenchyme. Smad7 deficiency led to a profound decrease in tooth size primarily due to a severely compromised cell proliferation capability in the dental epithelium. Consistent with the tooth shrinkage phenotype, RNA sequencing (RNA-seq) analysis revealed that Smad7 ablation downregulated genes referred to epithelial cell proliferation and cell cycle G1/S phase transition, whereas the upregulated genes were involved in responding to TGF-? signaling and cell cycle arrest. Among these genes, the expression of Cdkn1a (encoding p21), a negative cell proliferation regulator, was remarkably elevated in parallel with the diminution of Ccnd1 encoding the crucial cell cycle regulator cyclin D1 in the dental epithelium. Meanwhile, the expression level of p-Smad2/3 was ectopically elevated in the developing tooth germ of Smad7 null mice, indicating the hyperactivation of the canonical TGF-? signaling. These effects were reversed by addition of TGF-? signaling inhibitor in cell cultures of Smad7-/- molar tooth germs, with rescued expression of cyclin D1 and cell proliferation rate. In sum, our studies demonstrate that Smad7 functions primarily as a positive regulator of cell proliferation via inhibition of the canonical TGF-? signaling during dental epithelium development and highlight a crucial role for Smad7 in regulating tooth size.

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Dpysl4 is involved in tooth germ morphogenesis through growth regulation, polarization and differentiation of dental epithelial cells.

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Dpysl4 is involved in tooth germ morphogenesis through growth regulation, polarization and differentiation of dental epithelial cells.

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