Osteogenic protein-1 and related bone morphogenetic proteins regulate dendritic growth and the expression of microtubule-associated protein-2 in rat sympathetic neurons.

Osteogenic protein-1 (OP-1) is expressed in the developing nervous system and it has been found to induce dendritic growth in sympathetic neurons. To further characterize this phenomenon, the effects of OP-1 were compared to those of other members of the bone morphogenetic protein (BMP) family of growth factors. Recombinant human OP-1, BMP-6, BMP-2 and the Drosophila 60A protein induced dendritic growth in rat sympathetic neurons in a concentration-dependent manner with EC50-values of 1.8, 1.0, 1.7 and 2.7 ng/ml, respectively. In contrast, BMP-3 and cartilage-derived morphogenetic protein-2 (CDMP-2) as well as other classes of growth factors were inactive at concentrations up to 50 ng/ml. The dendritic growth induced by OP-1, BMP-6, BMP-2 and 60A was accompanied by increased expression of microtubule-associated protein-2 (MAP2) without changes in the expression of the phosphorylated forms of the M and H neurofilament subunits. These results suggest that several members of the BMP family have the capacity to regulate the morphological development of sympathetic neurons and that they may act by induction of specific cytoskeletal proteins.