Skeletal muscle atrophy is ameliorated in the SMAΔ7/Sam68^−/− mice. (A) Hematoxylin and eosin staining of triceps muscle sections from 10-dpp non-SMA, SMAΔ7/Sam68^+/+, and SMAΔ7/Sam68^−/− (SMA) mice. Bar, 100 µm. (B) Frequency distribution of muscle fiber areas (at least 2,000 for each genotype) of the experimental animals described in A. The colored lines and dotted line (non-SMA mice) represent the median value for each genotype: non-SMA mice (n = 3) median size = 531 µm² and fiber size (mean ± SEM) = 568.76 ± 5.8 µm²; non-SMA/Sam68^−/− mice (n = 3) median size = 557 µm² and fiber size (mean ± SEM) = 586.60 ± 5.7 µm²; SMAΔ7/Sam68^+/+ median size = 327 µm² and fiber size (mean ± SEM) = 342.32 ± 3.1 µm²; and SMAΔ7/Sam68^−/− median size = 486 µm² and fiber size (mean ± SEM) = 503.59 ± 4.6 µm². Statistical analysis of the median values among groups was performed by one-way ANOVA test followed by Dunn’s multiple comparison posttest. (C) qPCR analysis of the expression of atrophy-related genes in quadriceps and lower leg muscles of mice described in B. Values (mean ± SD; n = 4) were normalized with Actin mRNA. Statistical analysis was performed by one-way ANOVA test followed by Bonferroni’s multiple comparison posttest. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant (P > 0.05). r.l., relative level.