Disturbed TrkB localization and phosphorylation upon BDNF stimulation are detected in Smn-deficient axon terminals. (A) Ratio of the area of the presynapse (through Synaptophysin-1 [SYP]) vs. postsynapse (ACh receptors through Bungarotoxin [BTX]) of NMJs in the Transversus abdominis anterior (TVA) of control and SMNΔ7 P10 animals (N = 4, n = 130; two-tailed unpaired t test, ****P ≤ 0.0001). (B) NMJs in the TVA muscle in control and SMNΔ7 P5 animals stained against TrkB (gray), SYP (magenta) and BTX (green), scale bar: 10 µm. Dotted line depicts outline of the presynapse (SYP signal). Normalized mean gray values of TrkB (N = 4, n = 62; Two-tailed unpaired t test, ****P ≤ 0.0001). (C) Western blot analysis of TrkB and p-TrkB levels in whole-cell lysates of control and Smn^−/−;SMN2 motoneurons that were unstimulated or 15 min BDNF stimulated. β-actin was used as loading control. (D) Unstimulated and 30 min BDNF stimulated NMJs in the TVA muscle of control and SMNΔ7 P5 animals stained against p-TrkB (gray), SYP (magenta), and BTX (green), scale bar: 10 µm. Dotted line depicts outline of the presynapse (SYP signal). Normalized mean gray values of p-TrkB (N = 3, n = 60; ANOVA Kruskal–Wallis, **P ≤ 0.01; ****P ≤ 0.0001). Data are presented as scatter dot plot with bar. Bars represent the mean ± SEM. Source data are available for this figure: SourceData FS1.