title: New insights into the molecular mechanism of multiple synostoses syndrome (SYNS): mutation within the GDF5 knuckle epitope causes noggin-resistance.
abstract: 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.
authors: Institute for Chemistry and Biochemistry, Free University Berlin, Berlin, Germany.
authors: Gerburg K
authors: GK
authors: Schwaerzer
authors: Christian
authors: C
authors: Hiepen
authors: Heinrich
authors: H
authors: Schrewe
authors: Joachim
authors: J
authors: Nickel
authors: Frank
authors: F
authors: Ploeger
authors: Walter
authors: W
authors: Sebald
authors: Thomas
authors: T
authors: Mueller
authors: Petra
authors: P
authors: Knaus
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D052004:Bone Morphogenetic Protein Receptors / Q000378:metabolism; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D000939:Epitopes / Q000235:genetics*; D055428:Growth Differentiation Factor 5 / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D055767:Immobilized Proteins / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000378:metabolism; D013577:Syndrome; D013580:Synostosis / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099176:Noggin Protein
chemical_list: D052004:Bone Morphogenetic Protein Receptors; D002352:Carrier Proteins; D000939:Epitopes; D055428:Growth Differentiation Factor 5; D055767:Immobilized Proteins; D050505:Mutant Proteins; D051785:Smad Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D000099176:Noggin Protein