Activity of 2 in DM1 myotubes. (A) Effect of 2 on r(CUG)exp-containing DMPK levels in DM1 myotubes as determined by RT-qPCR. Error bars represent SD, n = 3 biological replicates, ***P < 0.001 (one-way ANOVA). (B) Ability of 2 to rescue the MBNL1 exon 5 splicing defect. Error bars represent SD, n = 3 biological replicates, *P < 0.05, ***P < 0.001 (one-way ANOVA). (C) Representative images of r(CUG)exp-MBNL1 foci in DM1 myotubes treated with 2. (D) Quantification of r(CUG)exp-MBNL1 foci/nucleus. Error bars represent SD, n = 3 biological replicates, 40 nuclei counted per replicate, *P < 0.05 (t test).