Odontoblasts are a type of terminally differentiated matrix-secreting cells. A number of molecular mechanisms are involved in the differentiation of odontoblasts. Several studies demonstrated that Krüppel-like factor 4 (KLF4) promotes odontoblast differentiation via control of dentin sialophosphoprotein (DSPP). Because nuclear factor I-C (NFIC) is also known to control DSPP, we investigated the relationship between NFIC and KLF4 during odontoblast differentiation. Klf4 mRNA expression was significantly decreased in Nfic(-/-) pulp cells compared with wild type cells. In immunohistochemistry assays, dentin matrix protein 1 (Dmp1), and DSP protein expression was barely observed in Nfic(-/-) odontoblasts and dentin matrix. Nfic bound directly to the Klf4 promoter and stimulated Klf4 transcriptional activity, thereby regulating Dmp1 and DSPP expression during odontoblast differentiation. Nfic or Klf4 overexpression promoted mineralized nodule formation in MDPC-23 cells. In addition, Nfic overexpression also decreased Slug luciferase activity but augmented E-cadherin promoter activity via up-regulation of Klf4 in odontoblasts. Our study reveals important signaling pathways during dentinogenesis: the Nfic-Klf4-Dmp1-Dspp and the Nfic-Klf4-E-cadherin pathways in odontoblasts. Our results indicate the important role of NFIC in regulating KLF4 during dentinogenesis.
KEYWORDS: DSPP, Dentin, Dentinogenesis, Differentiation, Gene Regulation, KLF5, NFIC, Odontoblast, Signaling, Tooth Development