Dspp mutations disrupt mineralization homeostasis during odontoblast differentiation

The main pathological feature in isolated hereditary dentin disorders is the abnormality of dentin mineralization. Dentin sialophosphoprotein (DSPP) gene is the only identified causative gene for the disorders. The present study aims to explore the molecular association between Dspp mutations and the disrupted mineralization homeostasis during odontoblast differentiation. We generated lentivirus constructs with the mouse full-length wild type Dspp cDNA and 3 Dspp mutants and transfected them into mouse odontoblast-lineage cells (OLCs) which were then performed 21-day mineralization inducing differentiation. The formation of mineralized nodules was obviously fewer in mutants. Digital Gene Expression (DGE) showed that Dspp mutation affected the OLC differentiation in a degree. Further examination validated that Dspp (LV-Dspp) overexpressing OLCs possessed the ability to strictly orchestrate framework for mineralization inductors like Bmp2, Col1 and Runx2, and proliferative markers for mineralization like Alp and Ocn, as well as mineral homeostasis feedback regulators Mgp and Htra1. However, the missense mutation in Dspp signal peptide region (LV-M2) and the nonsense mutation (LV-M5) broke this orchestration. The results suggested that the mutant Dspp disrupt the dynamic homeostasis of mineralization during OLC differentiation. We are the first to use full-length mouse Dspp gene expression system to explore the mineralization mechanism by which inductors and inhibitors adjust each other during odontoblast differentiation. Our findings shed new light on association between Dspp and the dynamic homeostasis of mineralization inductors and inhibitors, and indicate the disruption of mineralization homeostasis might be a crucial reason for Dspp mutations resulting in dentin disorders.