MAP2K1 and infection: Infection with AAV‐MEL apparently involved every muscle fiber and significantly increased MW/BW (Supporting Information, TableS1) and CSA of U7 muscles compared with sham‐infected and EV‐infected ones (Figure4B; P ≤ 0.01, ANOVA), without apparently affecting the relative percentage of fast and slow fiber populations and My heavy chains (Supporting Information, FigureS3).