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-induced 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.
"Chordin-like 1 (CHRDL1), also known as neuralin-1 (Coffinier et al., 2001), ventroptin (Sakuta et al., 2001) and neurogenesin-1 (Ueki et al., 2003), is a secreted BMP-binding protein that contains three von Willebrand type C repeats with homology to chordin (Nakayama et al., 2001). Direct interaction of CHRDL1 with BMP4 has been demonstrated by several groups, and weaker interactions with other BMPs and TGF-beta superfamily members have also been described (Nakayama et al., 2001; Sakuta et al., 2001; Chandra et al., 2006; Kane et al., 2008). Inhibition of BMP4 activity by CHRDL1 has been demonstrated in vivo by the ability of exogenous CHRDL1 to induce secondary axis formation in Xenopus embryos, which was rescued by co-injection by BMP4 (Nakayama et al., 2001; Sakuta et al., 2001), and in vitro by antagonizing the inhibitory effect of BMP4 in angiogenesis assays (Kane et al., 2008). "
[Show abstract][Hide abstract] ABSTRACT: Chordin-like 1 (CHRDL1) is a secreted bone morphogenetic protein (BMP) antagonist expressed in mesenchymal tissues whose function in development of the skeleton has not been examined in detail. Here we show Chrdl1 is dynamically expressed in the early distal limb bud mesenchyme, with expression becoming downregulated as development proceeds. Chrdl1 expression is largely excluded from the critical signaling center of the posterior limb bud, the Zone of Polarizing Activity (ZPA), as has been described for the BMP antagonist Gremlin (GREM1) (Scherz et al., 2004). Unlike Grem1, Chrdl1 is expressed in the hindlimb by a small subset of ZPA cells and their descendants suggesting divergent regulation and function between the various BMP antagonists. Ectopic expression of Chrdl1 throughout the avian limb bud using viral misexpression resulted in an oligodactyly phenotype with loss of digits from the anterior limb, although the development of more proximal elements of the zeugopod and stylopod were unaffected. Overgrowths of soft tissue and syndactyly were also observed, resulting from impaired apoptosis and failure of the anterior mesenchyme to undergo SOX9-dependent chondrogenesis, instead persisting as an interdigital-like soft tissue phenotype. Sonic hedgehog (Shh) and fibroblast growth factor (Fgf) signaling were upregulated and persisted later in development, however these changes were only detected late in limb development at timepoints when endogenous Grem1 would normally be downregulated and increasing BMP signaling would cause termination of Shh and FGF expression. Our results suggest that the early stages of the GREM1-SHH-FGF signaling network are resistant to Chrdl1-overexpression, leading to normal formation of proximal limb structures, but that later Bmp expression, impaired by ectopic CHRDL1, is essential for formation of the correct complement of digits.
[Show abstract][Hide abstract] ABSTRACT: Isoflavones are rich in soybean and are known to affect bone formation. This study examined the effects and modes of action of isoflavones on the differentiation of C2C12 myoblasts in the presence of the bone morphogenetic protein (BMP)-4.
The Journal of the Korean Orthopaedic Association 08/2007; 42(4). DOI:10.4055/jkoa.2007.42.4.537
[Show abstract][Hide abstract] ABSTRACT: We identified a gene encoding a novel secreted protein in mice and humans and named it Brorin. Mouse Brorin consists of 324 amino acids with a putative secreted signal sequence at its amino terminus and two cysteine-rich domains in its core region. Positions of 10 cysteine residues in the domains of Brorin are similar to those in the cysteine-rich domains of members of the Chordin family. However, the amino acid sequence of Brorin is not significantly similar to that of any other member of the Chordin family, indicating that Brorin is a unique member of the family. Mouse Brorin protein produced in cultured cells was efficiently secreted into the culture medium. The protein inhibited the activity of bone morphogenetic protein 2 (BMP2) and BMP6 in mouse preosteoblastic MC3T3-E1 cells. Mouse Brorin was predominantly expressed in neural tissues in embryos and also predominantly expressed in the adult brain. In the brain, the expression was detected in neurons, but not glial cells. The neural tissue-specific expression profile of Brorin is quite distinct from that of any other member of the Chordin family. Brorin protein promoted neurogenesis, but not astrogenesis, in mouse neural precursor cells. The present findings indicate that Brorin is a novel secreted BMP antagonist that potentially plays roles in neural development and functions.
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