Microtubule-associated Protein 1b, a Neuronal Marker Involved in Odontoblast Differentiation

• Maurin Jean-Christophe
• Couble Marie-Lise
• Staquet Marie-Jeanne
• Carrouel Florence
• About Imad
• Avila Jesús
• Magloire Henry
• Bleicher Françoise

• Fragile X mental retardation protein
• Human tooth pulp
• MAP-1B
• MAP2
• Odontoblasts
• Tau

Introduction: Map-1B belongs to the family of proteins that govern the dynamic state and organization of microtubules within cells. MAP-1B is a microtubuleassociated protein highly expressed during the development of the nervous system. Its expression, regulated by the fragile X mental retardation protein (FMRP), is essential to stabilize microtubules during the elongation of dendrites and neurites. Other microtubules-associated molecules such as tau or MAP2 seem to act similarly. The aim of this work was to identify the MAP-1B expression in in vitro and in vivo human odontoblasts during development and carious processes. The expression of MAP2 and tau was also studied. Materials and Methods: In cultured cells, MAP-1B expression was analyzed by real-time polymerase chain reaction, flow cytometry, and Western blot. Its distribution was visualized by in situ hybridization and immunochemistry both in vitro and in vivo. The expression of FMRP, MAP2, and tau was identified by real-time polymerase chain reaction and immunochemistry. Results: MAP-1B is specifically expressed in odontoblasts from adult third molars as well as incisor germs from human embryos. In adult carious teeth, it is also expressed in newly differentiated dentin-forming cells. In vitro, MAP-1B expression is related to the differentiation state of odontoblasts. MAP-1B clearly underlines the cellular architecture of cell bodies and processes of differentiated cells. FMRP, MAP2, and tau are also detected in vivo. Conclusion: On the basis of these data, MAP-1B could be considered as a new protein involved in the terminal differentiation of odontoblasts.