| First Author | Schwaerzer GK | Year | 2012 |
| Journal | J Bone Miner Res | Volume | 27 |
| Issue | 2 | Pages | 429-42 |
| PubMed ID | 21976273 | Mgi Jnum | J:299317 |
| Mgi Id | MGI:6492414 | Doi | 10.1002/jbmr.532 |
| Citation | Schwaerzer GK, et al. (2012) New insights into the molecular mechanism of multiple synostoses syndrome (SYNS): mutation within the GDF5 knuckle epitope causes noggin-resistance. J Bone Miner Res 27(2):429-42 |
| abstractText | Growth and differentiation factor 5 (GDF5), a member of the bone morphogenetic protein (BMP) family, is essential for cartilage, bone, and joint formation. Antagonists such as noggin counteract BMP signaling by covering the ligand's BMP type I (BMPRI) and type II (BMPRII, ActRII, ActRIIB) interaction sites. The mutation GDF5-S94N is located within the BMPRII interaction site, the so-called knuckle epitope, and was identified in patients suffering from multiple synostoses syndrome (SYNS). SYNS is characterized by progressive symphalangism, carpal/tarsal fusions, deafness and mild facial dysmorphism. Here we present a novel molecular mechanism of a GDF5 mutation affecting chondrogenesis and osteogenesis. GDF5-S94N exhibits impaired binding to BMPRII causing alleviated Smad and non-Smad signaling and reduced chondrogenic differentiation of ATDC5 cells. Surprisingly, chondrogenesis in mouse micromass cultures was strongly enhanced by GDF5-S94N. By using quantitative techniques (SPR, reporter gene assay, ALP assay, qPCR), we uncovered that this gain of function is caused by strongly reduced affinity of GDF5-S94N to the BMP/GDF antagonist noggin and the consequential lack of noggin inhibition. Thus, since noggin is upregulated during chondrogenic differentiation, GDF5-S94N exceeds the GDF5 action, which results in the phenotypic outcome of SYNS. The detailed molecular characterization of GDF5-S94N as a noggin-resistant growth factor illustrates the potential of GDF5 mutants in applications with defined therapeutical needs. |
