Bone morphogenetic protein-2, but not bone morphogenetic protein-7, promotes dendritic growth and calbindin phenotype in cultured rat striatal neurons

Bone morphogenetic proteins are members of the transforming growth factor-b eta superfamily. They are widely expressed in the mammalian nervous system, where thr) evert trophic effects on several neuronal populations. We studi ed the neurotrophic activity of bone morphogenetic protein-2 and bone morph ogenetic protein-7 (also called osteogenic protein-1) on cultured striatal cells, previously shown to express bone morphogenetic protein ligands and r eceptors. Our results indicate that only bone morphogenetic protein-2 promo ted the differentiation of GABAergic neurons, especially of the calbindin-p ositive subpopulation, the subset of projecting striatal neurons that degen erates in Huntington's disease. Bone morphogenetic protein-2 increased the area. perimeter and degree of arborization of GABAergic neurons, promoting calbindin phenotype without altering proliferation or apoptosis. In contras t, neither boar morphogenetic protein-2 nor -7 affected striatal cholinergi c interneurons. However, they both increased the number of glial fibrillar? ; acidic protein-positive cells. Suppression of glial proliferation with 5- fluorodeoxyuridine did not abolish bone morphogenetic protein-2 effects on the differentiation of striatal neurons, ruling out an indirect mechanism t hrough astrocytes. In conclusion, our results show that bone morphogenetic protein-2 promotes the differentiation of cultured GABAergic striatal neurons, suggesting that bone morphogenetic proteins are involved in the development of the striatu m. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.