Generation of Mice Supports Ameloblast-Specific Role for .

The identification and targeting of the molecular pathways regulating amelogenesis is an ongoing challenge in dental research, and progress has been restricted by the limited number of genetic tools available to study gene function in ameloblasts. Here, we generated 4 transgenic -driver mouse lines that express improved ()-recombinase from the locus of the mouse ameloblast-specific gene amelogenin X () with a large (250-kb) bacterial artificial chromosome DNA vector. All 4 transgenic lines were bred with ROSA26 reporter mice to characterize the developmental pattern with the gene encoding β-galactosidase enzyme activity assay and protein immunohistochemistry. From the 4 generated transgenic lines, 2 were selected for further analysis because they expressed a high amount of recombinase exclusively in ameloblasts and showed developmental stage- and cell-specific β-galactosidase activity mimicking the endogenous amelogenin expression. To test the functionality of the selected transgenic models, we bred the 2 mice lines with stromal interaction molecule 1 () floxed mice to generate ameloblast-specific conditional knockout mice (). STIM1 protein serves as one of the main calcium sensors in ameloblasts and plays a major role in enamel mineralization and ameloblast differentiation. mice displayed exclusive CRE-mediated recombination in incisor and molar ameloblasts. mice showed a severely defected enamel phenotype, including reduced structural integrity concomitant with increased attrition and smaller teeth. The phenotype and genotype of the showed significant differences with the previously reported -/, highlighting the need for cell- and stage-specific lines for an accurate phenotype-genotype comparison. Furthermore, our model has the advantage of carrying the entire gene locus rather than being limited to an partial promoter construct, which greatly enhances the stability and the specificity of our expression. As such, the transgenic lines that we developed may serve as a powerful tool for targeting ameloblast-specific gene expression in future investigations.