Mutations in GDF5 Reveal a Key Residue Mediating BMP Inhibition by NOGGIN
Open Access
- 26 November 2009
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Genetics
- Vol. 5 (11), e1000747
- https://doi.org/10.1371/journal.pgen.1000747
Abstract
Signaling output of bone morphogenetic proteins (BMPs) is determined by two sets of opposing interactions, one with heterotetrameric complexes of cell surface receptors, the other with secreted antagonists that act as ligand traps. We identified two mutations (N445K,T) in patients with multiple synostosis syndrome (SYM1) in the BMP–related ligand GDF5. Functional studies of both mutants in chicken micromass culture demonstrated a gain of function caused by a resistance to the BMP–inhibitor NOGGIN and an altered signaling effect. Residue N445, situated within overlapping receptor and antagonist interfaces, is highly conserved among the BMP family with the exception of BMP9 and BMP10, in which it is substituted with lysine. Like the mutant GDF5, both BMPs are insensitive to NOGGIN and show a high chondrogenic activity. Ectopic expression of BMP9 or the GDF5 mutants resulted in massive induction of cartilage in an in vivo chick model presumably by bypassing the feedback inhibition imposed by endogenous NOGGIN. Swapping residues at the mutation site alone was not sufficient to render Bmp9 NOG-sensitive; however, successive introduction of two additional substitutions imparted high to total sensitivity on customized variants of Bmp9. In conclusion, we show a new mechanism for abnormal joint development that interferes with a naturally occurring regulatory mechanism of BMP signaling. The development of the human skeleton is regulated by intricate signaling pathways involving secreted molecules that bind to cell surface receptors to elicit a response in the target cell. Bone morphogenetic proteins (BMPs) are an important part of this process. Their signaling capacity is regulated on several levels including the extracellular space where inhibitors such as Noggin prevent BMPs from binding to their cognate receptors. We here describe that specific mutations of a single amino acid in GDF5, a member of the BMP family, cause congenital fusion of joints. Investigating the effect of the mutation in detail, we can show that the mutant GDF5 is no longer inhibited by Noggin, thus providing a functional explanation for the patients' phenotype. Furthermore, we show that the mutated residue (N445) is conserved throughout the BMP family, with the exception of BMP9 and BMP10, that carry the same amino acid at this position as the mutant GDF5. Both are, just as the mutant, resistant to inhibition by Noggin. Variants of BMPs that are insensitive to antagonists may induce bone formation more effectively, providing a source for effective, low-dose therapeutics for clinical applications.Keywords
This publication has 43 references indexed in Scilit:
- Crystal structure analysis reveals a spring-loaded latch as molecular mechanism for GDF-5–type I receptor specificityThe EMBO Journal, 2009
- Myostatin in tendon maintenance and repairGrowth Factors, 2009
- Novel point mutations in GDF5 associated with two distinct limb malformations in Chinese: brachydactyly type C and proximal symphalangismJournal of Human Genetics, 2008
- Brachydactyly type A2 associated with a defect in proGDF5 processingHuman Molecular Genetics, 2008
- A New Subtype of Brachydactyly Type B Caused by Point Mutations in the Bone Morphogenetic Protein Antagonist NOGGINAmerican Journal of Human Genetics, 2007
- Generation of transgenic tendon reporters, ScxGFP and ScxAP, using regulatory elements of the scleraxis geneDevelopmental Dynamics, 2007
- Crystal structure of recombinant human growth and differentiation factor 5: Evidence for interaction of the type I and type II receptor-binding sitesBiochemical and Biophysical Research Communications, 2005
- UCSF Chimera?A visualization system for exploratory research and analysisJournal of Computational Chemistry, 2004
- Coordinated Expression of Noggin and Bone Morphogenetic Proteins (BMPs) During Early Skeletogenesis and Induction of Noggin Expression by BMP-7Journal of Bone and Mineral Research, 1999
- Crystal structure of human bone morphogenetic protein-2 at 2.7 Å resolution 1 1Edited by R. HuberJournal of Molecular Biology, 1999