Crosstalk between Nuclear Factor I-C and Transforming Growth Factor-β1 Signaling Regulates Odontoblast Differentiation and Homeostasis

Abstract

Transforming growth factor-β1 (TGF-β1) signaling plays a key role in vertebrate development, homeostasis, and disease. Nuclear factor I-C (NFI-C) has been implicated in TGF-β1 signaling, extracellular matrix gene transcription, and tooth root development. However, the functional relationship between NFI-C and TGF-β1 signaling remains uncharacterized. The purpose of this study was to identify the molecular interactions between NFI-C and TGF-β1 signaling in mouse odontoblasts. Real-time polymerase chain reaction and western analysis demonstrated that NFI-C expression levels were inversely proportional to levels of TGF-β1 signaling molecules during in vitro odontoblast differentiation. Western blot and immunofluorescence results showed that NFI-C was significantly degraded after TGF-β1 addition in odontoblasts, and the formation of the Smad3 complex was essential for NFI-C degradation. Additionally, ubiquitination assay results showed that Smurf1 and Smurf2 induced NFI-C degradation and polyubiquitination in a TGF-β1-dependent manner. Both kinase and in vitro binding assays revealed that the interaction between NFI-C and Smurf1/Smurf2 requires the activation of the mitogen-activated protein kinase pathway by TGF-β1. Moreover, degradation of NFI-C induced by TGF-β1 occurred generally in cell types other than odontoblasts in normal human breast epithelial cells. In contrast, NFI-C induced dephosphorylation of p-Smad2/3. These results show that crosstalk between NFI-C and TGF-β1 signaling regulates cell differentiation and homeostatic processes in odontoblasts, which might constitute a common cellular mechanism.

The Role of NFIC in Regulating Odontoblastic Differentiation of Human Molar Stem Cells from Apical Papilla

“…It is generally believed that NFIC is one of the molecules known to be required for root formation-the key late event in tooth morphogenesis [12][13][14]. However most studies obtained conclusions based on experiments with other non-molar root tissues (such as jaw, incisor) or cell lines of mice [11]. In order to further explore the function of Nfic on root development, we use human young molar stem cells from apical papilla (SCAPs) as our research objectives, which can differentiate into the odontoblasts located in root portion to generate root dentin.…”

“…Approximately 2.0 Â 10 6 in vitro-expanded hSCAPs mixed with 40 mg hydroxyapatite ceramic particles (Bio Osteon, China) were transplanted subcutaneously into the dorsal surfaces of 10-week-old immunodeficient mice (CB-17/SCID; Vitalriver, China) according to a method reported previously [11]. Transplants were harvested 8 weeks after transplantation.…”

Transforming Growth Factor-ß1 (TGF-ß1) immunoreactivity in heterotopic grafts of adult dental apical papilla.

“…Our data demonstrate 16 cells in the transplant developed reactive tertiary or osteoid dentin occupying the entire transplant during the first week after transplantation and it was finally eliminated. This type of dentin is characterized by the loss of its tubular structure and the acquisition of a morphology similar to the bone has been described in various clinical and experimental conditions 21,22 , among them the trasplants 10,16,20 , and its appearance has been justified as the result of a reaction to exogenous factors, among which is the inflammatory reaction of the host 16 .…”

“…Among the molecules that regulate the final stages of odontogenesis, the transforming growth factors superfamily (TGF) stands out, specially the transforming growth factor-beta 1 (TGF-ß1). It is involved in several stages of embryogenesis such as dental amelogenesis, controlling the expression of matrix metalloproteinases [7][8] , in cementogenesis and the regeneration of adult periodontal tissue 9 , in the differentiation of the odontoblasts and secretion of the predentina 10 . Differentiated odontoblasts secrete TGF-ß1 and regulate its activity in an autocrine manner 11 .…”

New insights into the role of NF1 in cancer

“…Increase in TGF-β decreases the level of NF1-C due to its degradation. The degradation is dependent on interaction between NF1-C and phosphorylated Smad2/3 complex [53].…”