A point mutation in Fgf9 impedes joint interzone formation leading to multiple synostoses syndrome.
Human multiple synostoses syndrome (SYNS) is an autosomal dominant disorder characterized by multiple joint fusions. We previously identified a point mutation (S99N) in FGF9 that causes human SYNS3. However, the physiological function of FGF9 during joint development and comprehensive molecular portraits of SYNS3 remain elusive. Here, we report that mice harboring the S99N mutation in Fgf9 develop the curly tail phenotype and partially or fully fused caudal vertebrae and limb joints, which mimic the major phenotypes of SYNS3 patients. Further study reveals that the S99N mutation in Fgf9 disrupts joint interzone formation by affecting the chondrogenic differentiation of mesenchymal cells at the early stage of joint development. Consistently, the limb bud micromass culture (LBMMC) assay shows that Fgf9 inhibits mesenchymal cell differentiation into chondrocytes by downregulating the expression of Sox6 and Sox9. However, the mutant protein does not exhibit the same inhibitory effect. We also show that Fgf9 is required for normal expression of Gdf5 in the prospective elbow and knee joints through its activation of Gdf5 promoter activity. Signal transduction assays indicate that the S99N mutation diminishes FGF signaling in developmental limb joints. Finally, we demonstrate that the conformational change in FGF9 resulting from the S99N mutation disrupts FGF9/FGFR/heparin interaction, which impedes FGF signaling in developmental joints. Taken together, we conclude that the S99N mutation in Fgf9 causes SYNS3 via the disturbance of joint interzone formation. These results further implicate the crucial role of Fgf9 during embryonic joint development.
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.|Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, P.R. China.
Lingyun
L
Tang
Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, P.R. China.
Xiaolin
X
Wu
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.
Hongxin
H
Zhang
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.|Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Shunyuan
S
Lu
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.
Min
M
Wu
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.|Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Chunling
C
Shen
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.|Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, P.R. China.
Xuejiao
X
Chen
Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Yicheng
Y
Wang
Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Weigang
W
Wang
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.
Yan
Y
Shen
Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, P.R. China.
Mingmin
M
Gu
Department of Radiology and Department of Pathology of Rui-Jin Hospital, SJTUSM, Shanghai, P.R. China.
Xiaoyi
X
Ding
Department of Radiology and Department of Pathology of Rui-Jin Hospital, SJTUSM, Shanghai, P.R. China.
Xiaolong
X
Jin
Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Jian
J
Fei
State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine, Rui-Jin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, P.R. China.|Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, P.R. China.|Shanghai Research Center for Model Organisms, Shanghai, P.R. China and.
Zhugang
Z
Wang
D000818:Animals; D002348:Carpal Bones / Q000002:abnormalities* / Q000503:physiopathology; D002454:Cell Differentiation / Q000235:genetics*; D020219:Chondrogenesis / Q000235:genetics; D051525:Fibroblast Growth Factor 9 / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D005532:Foot Deformities, Congenital / Q000235:genetics* / Q000503:physiopathology; D018507:Gene Expression Regulation, Developmental; D055428:Growth Differentiation Factor 5 / Q000235:genetics; D006228:Hand Deformities, Congenital / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D007596:Joints / Q000254:growth & development / Q000473:pathology; D051379:Mice; D017354:Point Mutation; D011487:Protein Conformation; D055758:SOX9 Transcription Factor / Q000235:genetics; D055755:SOXD Transcription Factors / Q000235:genetics; D015398:Signal Transduction; D013199:Stapes / Q000002:abnormalities* / Q000503:physiopathology; D013580:Synostosis / Q000235:genetics* / Q000503:physiopathology; D013639:Tarsal Bones / Q000002:abnormalities* / Q000503:physiopathology
C496459:FGF9 protein, human; C496460:Fgf9 protein, mouse; D051525:Fibroblast Growth Factor 9; C525894:Gdf5 protein, mouse; D055428:Growth Differentiation Factor 5; D055758:SOX9 Transcription Factor; D055755:SOXD Transcription Factors; C095939:Sox6 protein, mouse; C527933:Sox9 protein, mouse