Tooth-specific expression conferred by the regulatory sequences of rat dentin sialoprotein gene in transgenic mice

We have isolated a 3.8-kb DNA fragment containing the 5' flanking region, 1st exon, and 1st intron of the rat dentin sialoprotein (rDsp) gene and produced transgenic mice carrying a LacZ reporter gene under the control of this fragment. Expression of the transgene transcript and beta-galactosidase activity were restricted to dentin and odontoblasts with spatial and temporal patterns comparable to those of the endogenous mouse Dsp transcript, although beta-galactosidase activity could not be detected visually during embryonal stages. Other tissues tested, such as alveolar bones, ameloblasts and dental pulps, did not express the transgene. This indicates that the regulatory elements necessary for tooth-specific expression are present in the fragment, which contains a TATA box and several consensus sequences for binding sites of transcription factors related to tooth development, such as TCF-1/LEF-1, MSX-1 and Dlx-1. The regulatory sequences and the transgenic mice described here provide useful information for the study of tooth development.