Figure 9: Muscle-specific knockout of Fgf9 in mice (Fgf9^cKO) resulted in larger superstructures and increased number of acetylcholine receptor (AChR) clusters in the deltoid muscle.

MicroCT scans of 8 week (A) WT and (E) Fgf9^cKO mice show a significantly larger DT (DT;red) and lateral supracondylar ridge (LSR; yellow) in Fgf9^cKO mice. Histology of the DT support this phenotype (B, F). Skeletal muscle specificity of Acta1-Cre was confirmed using Ai14 reporters (H,G). Gene expression of (I) Agrn (p = 0.0287) and (J) Ikbkb (p = 0.0675) were increased in Fgf9^cKO deltoid muscle compared to WT muscle at 8 weeks of age (ΔCT calculated using average reference gene CT of ipo8 and Rn18s). Immunofluorescence (IF) was used to visualize nerves (neurofilament, green) and AChR clusters at neuromuscular junctions (α-bungarotoxin, red) in (K) WT and (L) Fgf9^cKO mice. At 3 weeks postnatally, Fgf9^cKO mice had significantly higher (N) AchR density than WT littermates and (M) more AChR. Data shown are biological replicates, mean ± SD. Lines in C, D, I, and N indicate significance (p < 0.05).