FGF9 monomer-dimer equilibrium regulates extracellular matrix affinity and tissue diffusion.
The spontaneous dominant mouse mutant, Elbow knee synostosis (Eks), shows elbow and knee joint synosotsis, and premature fusion of cranial sutures. Here we identify a missense mutation in the Fgf9 gene that is responsible for the Eks mutation. Through investigation of the pathogenic mechanisms of joint and suture synostosis in Eks mice, we identify a key molecular mechanism that regulates FGF9 signaling in developing tissues. We show that the Eks mutation prevents homodimerization of the FGF9 protein and that monomeric FGF9 binds to heparin with a lower affinity than dimeric FGF9. These biochemical defects result in increased diffusion of the altered FGF9 protein (FGF9(Eks)) through developing tissues, leading to ectopic FGF9 signaling and repression of joint and suture development. We propose a mechanism in which the range of FGF9 signaling in developing tissues is limited by its ability to homodimerize and its affinity for extracellular matrix heparan sulfate proteoglycans.
Harada
Masayo
M
RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
Murakami
Hirotaka
H
Okawa
Akihiko
A
Okimoto
Noriaki
N
Hiraoka
Shuichi
S
Nakahara
Taka
T
Akasaka
Ryogo
R
Shiraishi
Yo-Ichi
Y
Futatsugi
Noriyuki
N
Mizutani-Koseki
Yoko
Y
Kuroiwa
Atsushi
A
Shirouzu
Mikako
M
Yokoyama
Shigeyuki
S
Taiji
Makoto
M
Iseki
Sachiko
S
Ornitz
David M
DM
Koseki
Haruhiko
H
D000818:Animals; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004058:Diffusion; D005109:Extracellular Matrix / Q000378:metabolism*; D051525:Fibroblast Growth Factor 9 / Q000235:genetics / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000502:physiology; D011485:Protein Binding; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013580:Synostosis / Q000235:genetics; D014018:Tissue Distribution
C496460:Fgf9 protein, mouse; D051525:Fibroblast Growth Factor 9; D019812:Heparan Sulfate Proteoglycans