Institut de Biologie Médicale, INSERM U 424, Strasbourg, France.
Odontoblasts are post-mitotic, neural crest-derived, cells which overtly differentiate according to tooth specific temporo-spatial patterns and secrete predentin-dentin components. Neither the timing nor the molecular mechanisms of their specification are known and the problem of their patterning in the developing jaws is far from being solved. On the other hand, some significative strides were made concerning the control of their terminal differentiation. Fibronectin interacting with a 165 kDa, non integrin, membrane protein intervenes in the cytoskeletal reorganization involved in odontoblast polarization and their terminal differentiation can be triggered in vitro by immobilized members of the TGF beta family. Histological aspects and the transcriptional phenotypes (transcripts of TGF beta s, BMPs, msxs, IGF1, fibronectin, osteonectin, bone sialoprotein genes) are very similar in vivo and in vitro. In vivo members of the TGF beta super family secreted by preameloblasts, trapped and activated by basement membrane associated components, might initiate odontoblast terminal differentiation.