Regulation of Calbindin-D 28k Expression by Msx2 in the Dental Epithelium

Amelogenesis involves the coordinated expression of a set of molecules that includes enamel matrix proteins and calcium-binding proteins. Msx2 is a member of the divergent homeobox gene family and is instrumental in dental morphogenesis and biomineralization. This study focused on an EF-hand calcium-binding protein, calbindin-D(28k), which is highly expressed in dental epithelium. In vivo data showed that calbindin-D(28k) levels were higher in ameloblasts from Msx2(+/-) mice than Msx2(+/+) mice. Consistent with this finding, calbindin-D(28k) distribution was affected in transgenic mice with ectopic expression in root epithelium in rests of Malassez in Msx2(+/-) and more clearly in Msx2(-/-) mice. In accordance with these in vivo data, calbindin-D(28k) protein and mRNA levels were decreased in LS8 ameloblast-like cells by exogenous Msx2 overexpression. Furthermore, calbindin-D(28k) promoter activity (nt-1075/+34) was specifically diminished in the presence of Msx2 overexpression, showing that Msx2 behave as a transcriptional repressor for calbindin-D(28k) gene expression. In conclusion, Msx2 may control the spatiotemporally restricted frame of calbindin-D(28k) production in the dental epithelium in relation to enamel mineralization, as previously shown for amelogenin.