Abstract

Amelogenesis imperfecta is a congenital form of enamel hypoplasia. Although a number of genetic mutations have been reported in humans, the regulatory network of these genes remains mostly unclear. To identify signatures of biological pathways in amelogenesis imperfecta, we conducted bioinformatic analyses on genes associated with the condition in humans. Through an extensive search of the main biomedical databases, we found 56 genes in which mutations and/or association/linkage were reported in individuals with amelogenesis imperfecta. These candidate genes were further grouped by function, pathway, protein–protein interaction, and tissue-specific expression patterns using various bioinformatic tools. The bioinformatic analyses highlighted a group of genes essential for extracellular matrix formation. Furthermore, advanced bioinformatic analyses for microRNAs (miRNAs), which are short non-coding RNAs that suppress target genes at the post-transcriptional level, predicted 37 candidates that may be involved in amelogenesis imperfecta. To validate the miRNA–gene regulation association, we analyzed the target gene expression of the top seven candidate miRNAs: miR-3195, miR-382-5p, miR-1306-5p, miR-4683, miR-6716-3p, miR-3914, and miR-3935. Among them, miR-1306-5p, miR-3195, and miR-3914 were confirmed to regulate ameloblast differentiation through the regulation of genes associated with amelogenesis imperfecta in AM-1 cells, a human ameloblastoma cell line. Taken together, our study suggests a potential role for miRNAs in amelogenesis imperfecta.

Highlights

  • Mutations in COL17A1, DLX3, GALNT3, GJA1, ITGB4, LAMA3, LAMB3, and TP63, which are expressed in epithelial cells, are responsible for amelogenesis imperfecta as well as other ectodermal defects

  • Several amelogenesis imperfecta-associated genes (CLDN6, CLDN9, COL17A1, GJA1, ITGB4, and ITGB6) are grouped into the cell adhesion molecules, which are important for ectodermal functions

  • This suggests that tissue–tissue interactions contribute to proper ameloblast differentiation and function and that dysregulation of these genes is associated with the pathogenesis of amelogenesis imperfecta

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Summary

Introduction

95% of hydroxyapatite crystals (mainly calcium and phosphate, and magnesium, potassium, fluoride, and sodium), with the remaining consisting of matrix proteins and water [1,2,3]. Ameloblasts secrete an enamel matrix during amelogenesis, which comprises a pre-secretory (inductive), secretory, and maturation stage [1,4,5]. During the pre-secretory stage, inner enamel epithelial cells on the dentin matrix differentiate into ameloblasts. At the subsequent secretory stage, polarized ameloblasts with Tomes’ process start to secrete enamel matrix proteins such as ameloblastin (AMBN), amelogenin (AMELX), amelotin (AMTN), and enamelin (ENAM). These enamel matrix proteins are phosphorylated by extracellular serine/threonine protein kinase FAM20C and cleaved by metallopeptidase 20

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