While QKO SC mice on P30 showed a high fraction of myofibers containing central nuclei (Fig. 4e and Supplementary information, Fig. S7e), this histological abnormality was milder with ages, consistent with a phenotype in another DM1 mouse model generated by overexpression of CUGBP1.59 Meanwhile, fiber type analysis showed an increased percentage and a decreased CSA of type I myofibers in DSMD-QKO SC mice (Fig. 4f). This evidence concerns the gene CELF1 and myotonic dystrophy type 1.