Advisory Committee Chair
Advisory Committee Members
Date of Award
Degree Name by School
Master of Science in Dentistry (MScD) School of Dentistry
Pleiotrophin (PTN) is an extracellular matrix-associated growth factor and chemokine expressed in mesodermal and ectodermal cells. It plays an important role in osteoblast recruitment and differentiation. PTN has two well-known physiological receptors, protein tyrosine phosphatase beta/zeta (RPTPRZ1), and N-syndecan. Protein tyrosine phosphatases are a group of enzymes that remove phosphate groups from phosphorylated tyrosine residues on proteins. Protein tyrosine phosphorylation is a common post-translation modification that can create novel recognition motifs for protein interactions and cellular localization, affect protein stability and regulate enzyme activity. Osteoblasts have recently been found to express the short transmembrane isoform of RPTP beta/zeta but nothing is known regarding RPTP beta/zeta expression during tooth development. There is also very limited information available about PTN and RPTP expression during odontoblast differentiation and tooth formation, and thus we aimed to establish the spatiotemporal expression pattern of PTN and RPTP during mouse odontogenesis. Immortalized mouse dental pulp (MD10-A11), odontoblast-like (M06-G3), mesenchymal/preosteoblasts (C3H10t1/2) and mature mouse osteoblasts (ROS) cell lines were grown and samples prepared for immunocytochemistry, Western blot, and conventional PCR analysis. Finally, immunohistochemistry of sectioned mice mandibles and maxillaries at developmental stages E16, P3, P10 and P28 was performed. The experiments showed that PTN, at both the mRNA and protein level, was expressed in all tested cell lines. We observed initial expression of PTN in the inner enamel epithelium with prolonged expression in the ameloblasts and odontoblasts throughout their stages of maturation and strong expression in the terminally differentiated and enamel matrix-secreting ameloblasts and odontoblasts of the adult. RPTP was expressed at the mRNA level in all the cell lines investigated but at varying levels mainly as phosphacan (the extracellular domain of RPTP beta/zeta, and at the protein level RPTP was expressed in the mature MO6-G3 and ROS cells as Phosphacan short isoform (PSI), although the full-length form of Phosphacan cannot be ruled out at the present. These studies demonstrate that PTN and RPTP beta/zeta are expressed during tooth development. Localization of PTN and RPTP within mineralized tissue may indicate that both PTN and Phosphacan is involved in the production or homeostasis of mineralized tissue (bone and enamel).
Tamkenath, Amena, "Characterization of Pleiotrophin and Receptor Protein Tyrosine Phosphatase beta/zeta in Odontoblast and Osteoblast cell lines" (2012). All ETDs from UAB. 3098.