The use of animal models to explore amelogenin variants in amelogenesis imperfecta.

Amelogenin proteins are secreted by ameloblast cells during tooth development. Because of extensive alternative splicing of the amelogenin primary RNA transcript, and because systematic proteolysis results in many additional peptides during enamel maturation, it has been difficult to assign function to individual amelogenins. Targeted deletions and transgenic mice have been generated in order to better understand amelogenin protein function in vivo. From these murine models, we have determined that amelogenins are responsible for normal enamel thickness and structure, but not for initiation of enamel mineral formation at the dentin-enamel junction. Although it is now clear that the amelogenin (AmelX) gene exists in a nested orientation and that AmelX is expressed at a low level in various developing tissues, the significance of these findings is incompletely understood. Future studies are expected to answer remaining questions concerning structure/function relationships among these 'enamel proteins'.