Bone morphogenetic protein (BMP) antagonists regulate the pleiotropic actions of BMPs by binding to BMPs. We previously isolated the Neurogenesin-1 (Ng1) gene and found that Ng1 protein induces neuronal differentiation in the brain. In this study, we found that Ng1 was expressed in the primordial cells of the skeleton and investigated whether Ng1 protein inhibited the BMP action to induce osteoblastic differentiation in C2C12 myoblasts. Interestingly, Ng1 protein inhibited the BMP7-iriduced alkaline phosphatase activity while it did not inhibit the BMP2-induced activity. All, data suggest that Ng1 protein plays an important role in the embryonic bone formation by differentially regulating BMPs. (c) 2006 Elsevier Inc. All rights reserved.