DENTIN SIALOPROTEIN, DENTIN PHOSPHOPROTEIN, ENAMELYSIN AND AMELOBLASTIN - TOOTH-SPECIFIC MOLECULES THAT ARE DISTINCTIVELY EXPRESSED DURING MURINE DENTAL DIFFERENTIATION

Dentin sialophosphoprotein [designated DSPP and cleaved into dentin si aloprotein (DSP) and dentin phosphoprotein (DPP)I, enamelysin and amel oblastin are each expressed in unique fashions during tooth developmen t. It is possible that these components participate in cell differenti ation and the conversion of unmineralized matrix into mineralized stru ctures. In order to delineate the timing and the positioning of these three molecules in a physiological context, we compared their expressi on profiles by performing in situ hybridization experiments on consecu tive sections in developing mouse tissues. Hybridization signals were uniquely detected for DSPP mRNA in odontoblasts and preameloblasts, fo r enamelysin mRNA in odontoblasts and in the facing ameloblast layer, and for ameloblastin mRNA in preodontoblasts, polarizing odontoblasts and ameloblasts. Immunohistochemistry showed that DSP and ameloblastin transcripts were translated into proteins that were deposited at the apical pole of the differentiated cells (odontoblasts and ameloblasts, respectively). The interrelated expression profiles found for these t ooth-specific molecules illustrate the importance of a specific molecu lar network to initiate highly regulated processes such as cytodiffere ntiation and the subsequent mineralization.