AAV9-IGHMBP2 rescues the loss in lumbar motor neurons and innervations of gastrocnemius. (a) Nissl-stained (top) and ChAT immunostained (bottom) cross sections of lumbar spinal cord in low-dose-treated males at 8 weeks of age compared to those of age matched untreated and “Het” littermates (n = 4 for each group), scale bar = 50 m. (b) Motor neuron counts in the ventral horn of lumbar spinal cord demonstrate a significant increase in total number of motor neurons in treated nmd compared to untreated (1261 ± 219 in treated versus 788 ± 96 in untreated, one-way analysis of variance (ANOVA) P = 0.003; 2,133 ± 368 in “Het” versus 1,261 ± 219 in treated, one-way ANOVA P = 0.007). Error bars represent mean ± SEM. Degenerated motor neurons are indicated by arrow and excluded in quantification. (c) NMJs from gastrocnemius muscle of low-dose-treated males at 8 weeks of age compared to those of age-matched untreated and “Het” littermates (n = 4 for each group). Muscles were labeled with α-BTX for AChRs, anti-neurofilament, and anti-vesicular acetylcholine transporter (VAChT) for nerve terminals, scale bar = 20 m. (d) Percentage of innervated, partially innervated, and denervated muscles; % of fully innervated in treated 59.285 ± 4.38 versus 19.54 ± 3.48 in untreated (one-way ANOVA P < 0.0001). Error bars represent mean ± SEM.