Expression of Nfic during root formation in first mandibular molar of rat.

The transcription factor Nfic is a key regulator during tooth development. Nfic deficient mice exhibit short and abnormal molar roots and severely deformed incisors. Dental epithelial cells, known as Hertwig's epithelial root sheath (HERS), participate in root formation. However, whether Nfic is involved in HERS-mesenchyme interaction remains unclear. In this study, the detail temporal and spatial expression pattern of Nfic during rat molar development was examined using immunohistochemistry and in situ hybridization. Nfic was detected in ameloblasts, dental follicle cells (DFCs) and dental papilla cells (DPCs), especially the DPCs close to dentin, from postnatal day 5 to day 16. Nfic expression in DPCs, DFCs and HERS cells was also examined by western blot and RT-PCR. Nfic was detected in DPCs and DFCs, but not in HERS cells. Co-culture experiment further indicated that Nfic mRNA expression in DPCs was elevated by the presence of HERS cells. Our results revealed that Nfic could be a marker gene for root odontoblasts differentiation initiation and its expression might be regulated through epithelial-mesenchymal interaction.