A rat 8 kb dentin sialoprotein-phosphophoryn (DSP-PP) promoter directs spatial and temporal LacZ activity in mouse tissues

Abstract

Dentin sialoprotein (DSP) and phosphophoryn (PP) are two major dentin noncollagenous proteins that are encoded on a single DSP-PP transcript whose expression is tightly regulated during tooth dentinogenesis. The recent identification of this gene transcript in other tissues, including inner ear and jaw tissue, suggests that DSP and PP may have pleiotropic effects on other organs besides teeth. To identify candidate regulatory elements that control DSP-PP temporal and spatial expression, we constructed a -5 kb upstream region rat DSP-PP promoter into the beta-galactosidase expression vector pnLacF plasmid and used this construct to prepare DSP-PP-LacZ transgenic mice. Multiple mouse tissues including teeth, bone, and kidney obtained from the six resulting transgenic mouse lines displayed strong LacZ activity. This spatial distribution was confirmed in several of these tissues by in situ hybridization studies. LacZ activity was transiently expressed in preameloblasts and continuously expressed in odontoblasts demonstrating that this -5 kb rat promoter-dependent LacZ expression mimics reported DSP-PP mRNA expression patterns. Interestingly, this -5 kb rat promoter construct drives LacZ expression according to the rat developmental clock. Based on identified transcription factors present in this -5 kb promoter region, we have identified several probable cis-regulatory modules whose interaction with one another could account for the spatial and temporal distribution of DSP-PP transcripts in developing tissues.