Background: Recently, various amelogenesis imperfecta such as molar incisor hypomineralization (MIH) have been reported in pediatric dentistry. The cause has been studied extensively but is not yet clear. Therefore, dentists focus on prevention to avoid becoming serious. In order to find a new approach, we also need to understand the mechanism of enamel formation. The immature dental epithelial cells exist on the posterior side of the mouse incisor, while differentiated cells such as ameloblasts occur on the anterior side, since mouse incisors grow continuously. All ameloblast differentiation can be observed on the mouse incisor. Thus, the dental epithelium of the mouse incisor was analyzed to identify molecules that affect ameloblast differentiation in enamel formation. Results: Tgf superfamily genes, cell adhesion molecules, Wnt-related genes, and transcription factors such as homeobox genes were expressed in the dental epithelium of the mouse incisor. Furthermore, the expression levels of these molecules increased depending on the differentiation of the molar tooth germ. Site-specifically-expressed molecules were also observed in the frontal section of the incisor, concentrated at the enamel border. These may contribute to the morphology or play a role in crown-root determination. β1 integrin, fibronectin, Gdf5, and Sox2 were also analyzed to determine their function. These molecules were found to play important roles in ameloblast differentiation and tooth development. Conclusion: Various molecules were intricately involved in tooth development and morphogenesis in this study. Mouse incisors are a useful model system for the analysis of not only ameloblast differentiation, but also that of all epithelial tissues.
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