Bone morphogenetic proteins (BMPs) are multifunctional growth factors that belong to the transforming growth factor-beta superfamily. BMPs regulate several crucial aspects of embryonic development and organogenesis. Here, we demonstrate that BMP-2 inhibits the neurite outgrowth of postnatal cerebellar neurons in vitro. Although receptor-regulated Smad proteins are activated by BMP-2, this signal transduction is not necessary for the inhibitory effect of BMP-2. Interestingly, BMP-2 activates LIM-kinase 1 in the neurons, and the dominant negative form of LIM-kinase I abolishes the effect of BMP-2. Thus, BMP-2 inhibits neurite outgrowth by a LIM-kinase 1-dependent mechanism, and our findings add a new member to the group of neurite growth inhibitors. (c) 2007 Elsevier Inc. All rights reserved.