Journal: Nature genetics
Article Title: FGF9 monomer/dimer equilibrium regulates extracellular matrix affinity and tissue diffusion
doi: 10.1038/ng.316
Figure Lengend Snippet: Ectopic FGF9 Eks signaling due to its hyper diffusibility. ( a–e ) Increased diffusibility of FGF9 Eks in the skull bone anlagen. FGF9 WT or FGF9 Eks beads were implanted onto the coronal suture at E15 mice and Spp1 expression was examined by whole-mount in situ hybridization 24 hours after implantation. On the operated sides with FGF9 WT ( a ) and FGF9 Eks ( c ) bead implants, we observed well-defined intense signals in the frontal and parietal bone anlagen around the implants, which were not seen on the unoperated side ( b, d ). This domain with intense Spp1 signals reflects diffusibility of exogenous FGF9 proteins. We therefore compared diffusibility of FGF9 WT and FGF9 Eks based on the induced expression domain of Spp1 ( e ). The diffusion areas (%) in the frontal and parietal bone anlagen area were estimated from the area ratio of the intense Spp1 expression against the frontal and parietal bone anlagen. Data are represented as mean ± s.e.m. of six operations. FGF9 Eks is more diffusible than FGF9 WT . Significance was determined by two-tailed Student’s t -test. ( f–h ) Increased diffusibility of FGF9 Eks in the forelimb bud. FGF9 WT or FGF9 Eks beads were implanted into forelimb buds of Fgf9 −/− embryos of E10.5 mice. Diffusion of exogenous FGF9 WT ( f ) and FGF9 Eks ( g ) after 2 hours was immunodetected using a FGF9 antibody. ( h ) The diffusion area of FGF9 Eks and FGF9 WT was measured at the level of the equator of the beads. Data are represented as mean (FGF9 WT =100%) ± s.e.m. of four (FGF9 WT ) or five (FGF9 Eks ) operations. FGF9 Eks is also more diffusible than FGF9 WT in limb buds. Significance was determined by one-tailed Student’s t -test. ( i–x ) The downstream target genes of FGF signaling, Etv4 and Etv5 , are expressed ectopically in the prospective elbow joint in Fgf9 Eks/Eks mice. Counterstaining with Giemsa ( i, j, q, r ) and in situ detection of Col2a1 ( k, l, s, t ), Etv4 ( m, n, u, v ) and Etv5 ( o, p, w, x ) in the forelimb buds of Fgf9 +/+ and Fgf9 Eks/Eks embryos at E10.5 and E11.5. There was ectopic expression of Etv4 ( n, v ) and Etv5 ( p, x ), in the cartilaginous condensation including the prospective elbow joint position, which was demarcated as the gap of Col2a1 expression ( s , arrow), in Fgf9 Eks/Eks , which were not seen in Fgf9 +/+ mice ( m, o, u, w ). Scale bars, 100 µm. ( y ) A model for the pathogenic mechanism underlying elbow joint synosotsis in Fgf9 Eks/Eks mice. In Fgf9 Eks/Eks mice, ectopic FGF9 signaling due to hyper-diffusion of FGF9 Eks at the prospective elbow joint may inhibit the initiation of joint development. ( z ) A model for the pathogenic mechanism underlying premature fusion of the coronal suture in Fgf9 Eks/Eks mice. In Fgf9 Eks/Eks mice, ectopic FGF9 signaling due to hyper-diffusion of FGF9 Eks at the coronal suture may promote ectopic osteogenesis and subsequently induce premature fusion of the suture.
Article Snippet: Sections through the equator of the bead were analyzed for exogenous FGF9 using goat anti-human FGF9 antibody (R&D Systems) and a cell and tissue staining kit HRP-AEC system (R&D Systems).
Techniques: Expressing, In Situ Hybridization, Diffusion-based Assay, Two Tailed Test, One-tailed Test, In Situ