Cbfα1 hinders autophagy by DSPP upregulation in odontoblast differentiation

Odontoblasts forms dentin as the main hard tissue of the tooth. Autophagy is a highly conserved homeostasis involved in odontoblast differentiation. DSPP (Dentin sialophosphoprotein) and Cbfα1 (Core binding factor α1) are typical factors in odontoblasts of the dentin-pulp complex. However, the relationship between Cbfα1 and DSPP as well as the role of Cbfα1 involved in the autophagy during odontoblast differentiation are poorly understood. In this study, we found the stimulation with FGF2 in MDPC-23 cells resulted in the suppression of autophagy and promotion of cell differentiation. We demonstrated that both mRNA and protein levels of Cbfα1 and DSPP were elevated upon FGF2 stimulation coupled with the inhibition of autophagy in MDPC-23 cells. Further results revealed that overdose of Cbfα1 increased the expression of DSPP, and also suppressed autophagy in MDPC-23 cells. Using luciferase reporter assay and EMSA, we illustrated that Cbfα1 upregulated DSPP expression through binding to the specific sites 5'-TACCTCA (-3950 bp to -3944 bp) and 5'-ACCACA (-3106 bp to -3101 bp) in DSPP promoter. Furthermore, ChIP assay results revealed that FGF2 treatment enhanced this binding of Cbfα1 to DSPP promoter. Signaling pathway inhibitor screening further revealed Cbfα1 suppressed autophagy involved in Wnt I signaling. Moreover, knockdown of Cbfα1 using siRNA silencing approach reversed the FGF2-mediated suppression of autophagy in MDPC-23 cells. Thus, these findings illustrate a novel regulatory mechanism by which Cbfα1 transcriptionally enhances DSPP expression, and also provide an insight into the inhibitory action of Cbfα1 in autophagy thereby facilitating odontoblast differentiation upon FGF2 stimulation.