title: Activating and deactivating mutations in the receptor interaction site of GDF5 cause symphalangism or brachydactyly type A2.
abstract: Here we describe 2 mutations in growth and differentiation factor 5 (GDF5) that alter receptor-binding affinities. They cause brachydactyly type A2 (L441P) and symphalangism (R438L), conditions previously associated with mutations in the GDF5 receptor bone morphogenetic protein receptor type 1b (BMPR1B) and the BMP antagonist NOGGIN, respectively. We expressed the mutant proteins in limb bud micromass culture and treated ATDC5 and C2C12 cells with recombinant GDF5. Our results indicated that the L441P mutant is almost inactive. The R438L mutant, in contrast, showed increased biological activity when compared with WT GDF5. Biosensor interaction analyses revealed loss of binding to BMPR1A and BMPR1B ectodomains for the L441P mutant, whereas the R438L mutant showed normal binding to BMPR1B but increased binding to BMPR1A, the receptor normally activated by BMP2. The binding to NOGGIN was normal for both mutants. Thus, the brachydactyly type A2 phenotype (L441P) is caused by inhibition of the ligand-receptor interaction, whereas the symphalangism phenotype (R438L) is caused by a loss of receptor-binding specificity, resulting in a gain of function by the acquisition of BMP2-like properties. The presented experiments have identified some of the main determinants of GDF5 receptor-binding specificity in vivo and open new prospects for generating antagonists and superagonists of GDF5.
authors.affiliation: Institut für Medizinische Genetik, Charité, Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Seemann
authors.forename: Raphaela
authors.initials: R
authors.lastname: Schwappacher
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Kjaer
authors.forename: Deborah
authors.initials: D
authors.lastname: Krakow
authors.forename: Katarina
authors.initials: K
authors.lastname: Lehmann
authors.forename: Katherine
authors.initials: K
authors.lastname: Dawson
authors.forename: Sigmar
authors.initials: S
authors.lastname: Stricker
authors.forename: Jens
authors.initials: J
authors.lastname: Pohl
authors.forename: Frank
authors.initials: F
authors.lastname: Plöger
authors.forename: Eike
authors.initials: E
authors.lastname: Staub
authors.forename: Joachim
authors.initials: J
authors.lastname: Nickel
authors.forename: Walter
authors.initials: W
authors.lastname: Sebald
authors.forename: Petra
authors.initials: P
authors.lastname: Knaus
authors.forename: Stefan
authors.initials: S
authors.lastname: Mundlos
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000235:genetics / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D004628:Embryonic Structures / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology; D005385:Fingers / Q000000981:diagnostic imaging / Q000473:pathology*; D055428:Growth Differentiation Factor 5; D006801:Humans; D017403:In Situ Hybridization; D017880:Limb Deformities, Congenital / Q000235:genetics* / Q000473:pathology; D051379:Mice; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011859:Radiography; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D046509:Tissue Culture Techniques; D000099176:Noggin Protein
chemical_list: D052005:Bone Morphogenetic Protein Receptors, Type I; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D055428:Growth Differentiation Factor 5; D011994:Recombinant Proteins; D000099176:Noggin Protein; C525893:GDF5 protein, human; C525894:Gdf5 protein, mouse; C498214:BMPR1B protein, human