Dentin sialophosphoprotein expression in enamel is regulated by Copine-7, a preameloblast-derived factor

Dentin sialophosphoprotein (Dspp) is expressed in odontoblasts and transiently expressed in early ameloblasts. However, the origin of Dspp in ameloblasts remains unclear. Our previous studies demonstrated that copine-7 (CPNE7), a molecule that is secreted by the dental epithelium, is expressed in early ameloblasts and is then translocated to differentiating odontoblasts; its expression levels correlate with odontoblast differentiation under the control of Dspp expression. The objective of this study is to figure out the relationship between CPNE7 and Dspp during amelogenesis.

The gene expression patterns of CPNE7 and dentin sialoprotein (DSP) were examined by immunohistochemistry, western blot analysis, and real-time polymerase chain reaction. The effects of CPNE7 on Dspp regulation were investigated using luciferase and chromatin immunoprecipitation assays in ameloblastic HAT-7 cells.

The gene expression pattern of Cpne7 was similar to that of Dspp during ameloblast differentiation. Moreover, Gene expression omnibus profiles indicated that there is a close correlation between Cpne7 and Dspp expression in various normal human tissues. We also confirmed the effects of CPNE7 on the induction of Dspp in ameloblastic HAT-7 cells. Cpne7 overexpression promoted Dspp expression, whereas Dspp expression was down-regulated by Cpne7 inactivation.

These results suggest that the expression of Dspp in early amelogenesis is linked to CPNE7, a preameloblast-derived factor.