Transcriptional regulation of AMELX and DSPP genes by MIZ-1 and ZBTB5

Abstract

Amelogenin (AMELX) is the main component of the developing enamel matrix and is essential for enamel thickness and structure. Dentin sialophosphoprotein (DSPP) plays an important role in the differentiation of odontoblast and mineral deposition. We recently found that POK family proteins are expressed during tooth development. To identify which POK proteins are potentially involved in tooth development, we investigated mRNA expression profiles of POK proteins during odontoblastic differentiation of hDPSC (human dental pulp stem cell). The mRNA expression pattern is variable depending on the POK gene and temporally regulated during odontoblast differentiation. To investigate which POK proteins regulate mineralization of differentiated odontoblast cells, hDPSCs were transfected with expression vector of various POK proteins and siRNA against POK mRNA. Arizarin red staining of the odontoblast (day 11 or 12 after transfection) showed that MIZ-1, ZBTB2 significantly increased the mineral nodules but ZBTB5 decreased. We are in the process of investigating how POK family proteins regulate gene expression of AMELX and DSPP. In the mice MEF cells transfected with MIZ-1, ZBTB2 or ZBTB5 expression vectors, MIZ-1 increased but ZBTB5 repressed gene expression of Amelx and Dspp. However, ZBTB2 didn’t affect expression of the two genes. By reporter assays, we found that ZBTB5 repressed longer (bp, -485 to +100) and minimal promoters (bp, -70 to +100) of Amelx gene. MIZ-1 activated minimal promoter of Amelx gene, but repressed longer promoter of Amelx gene. ZBTB2 repressed only minimal promoter. Our preliminary data suggest that POK proteins regulate AMELX and DSPP gene expression.