| Dentinogenesis is a complex process of dentin formation. It involves differentiation of odontoblasts, the cells that make dentin, and the formation of a unique extracellular matrix, known as dentin. Dentin is ultimately produced through the interaction of collagen fibers, non-collagenous proteins and hydroxyapatite (HA) crystals. Odontoblasts are cranial neural crest (CNC) ectomesenchymal derived cells. Trps1 is a novel transcription factor believed to play an important role in both tooth formation and the mineralization process. TRPS1 gene mutations are known to result in dental and skeletal abnormalities manifested in humans as tricho-rhino-phalangeal syndrome (TRPS) and Ambras syndrome. Trps1 expression varies throughout odontoblast development. Strongly expressed in preodontoblasts, Trps1 then decreases in mature secretory cells at onset of mineralization; thus its downregulation coincides with terminal differentiation of odontoblasts. Our laboratory recently demonstrated that sustained high expression of Trps1 in secretory odontoblasts represses secretion and mineralization of dentin matrix in vitro. However, the specific role Trps1 plays in dentinogenesis remains unclear. To better understand the function of Trps1 in odontoblast maturation, ex vivo tooth organ culture studies were performed. Trps1 knockout mice (KO) are perinatal lethal, therefore dentinogenesis has not been studied in these mice until now. Analyses were performed to define whether Trps1-deficiency affects odontoblast maturation and/or odontoblast function. We found that Trps1 KO mice were able to form differentiated odontoblasts, capable of secreting a predentin matrix. However, mature odontoblasts in Trps1 KO mice were unable to produce matrix vesicles, an important component that supports the mineralization process. Altered expression of several key osteogenic factors (Runx2, Sp7, TNAP) in Trps1 KO tooth organs revealed that Trps1 functions in both a cell autonomous and non-autonomous fashion in different areas of the developing molar. Furthermore, analyses of embryonic day 18.5 Trps1 KO molars revealed Trps1-deficienct mice exhibit a smaller first mandibular molar compared to WT, mimicking a dental phenotype seen in human patients affected with TRPS. Results of this project have provided first insight into the role of Trps1 in odontoblast maturation and allowed for better understanding of the molecular mechanisms of dentin formation. |
