Targeted overexpression of amelotin disrupts the microstructure of dental enamel

• Published in: PloS one 2012-04, Vol.7 (4), p.e35200-e35200
• Main Authors: Lacruz, Rodrigo S, Nakayama, Yohei, Holcroft, James, Nguyen, Van, Somogyi-Ganss, Eszter, Snead, Malcolm L, White, Shane N, Paine, Michael L, Ganss, Bernhard
• Format: Article
• Language: English
• Subjects: AMBN protein; Ameloblasts; Ameloblasts - metabolism; Ameloblasts - pathology; Amelogenin; Amelogenin - genetics; Amelogenin - metabolism; Amino Acid Sequence; Animal genetic engineering; Animals; Biology; Cellular structure; Crystals; Dental enamel; Dental Enamel - pathology; Dental Enamel - ultrastructure; Dental Enamel Proteins - genetics; Dental Enamel Proteins - metabolism; Dentistry; Durapatite - chemistry; Enamel; Endoplasmic reticulum; Extracellular matrix; Genes; Genetically modified animals; Hydroxyapatite; Hydroxyapatites; Immunohistochemistry; In vivo methods and tests; Laboratories; Mechanical properties; Medicine; Mice; Mice, Transgenic; Microstructure; Molecular biology; Molecular Sequence Data; Polypeptides; Prisms; Promoter Regions, Genetic; Proteins; Rodents; Surface structure; Teeth; Transgenic animals; Transgenic mice
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0035200

We have previously identified amelotin (AMTN) as a novel protein expressed predominantly during the late stages of dental enamel formation, but its role during amelogenesis remains to be determined. In this study we generated transgenic mice that produce AMTN under the amelogenin (Amel) gene promoter to study the effect of AMTN overexpression on enamel formation in vivo. The specific overexpression of AMTN in secretory stage ameloblasts was confirmed by Western blot and immunohistochemistry. The gross histological appearance of ameloblasts or supporting cellular structures as well as the expression of the enamel proteins amelogenin (AMEL) and ameloblastin (AMBN) was not altered by AMTN overexpression, suggesting that protein production, processing and secretion occurred normally in transgenic mice. The expression of Odontogenic, Ameloblast-Associated (ODAM) was slightly increased in secretory stage ameloblasts of transgenic animals. The enamel in AMTN-overexpressing mice was much thinner and displayed a highly irregular surface structure compared to wild type littermates. Teeth of transgenic animals underwent rapid attrition due to the brittleness of the enamel layer. The microstructure of enamel, normally a highly ordered arrangement of hydroxyapatite crystals, was completely disorganized. Tomes' process, the hallmark of secretory stage ameloblasts, did not form in transgenic mice. Collectively our data demonstrate that the overexpression of amelotin has a profound effect on enamel structure by disrupting the formation of Tomes' process and the orderly growth of enamel prisms.