Figure 1. Systemic administration of 2′-O-(2-methoxyethyl) (MOE) ASOs in the HSA^LR transgenic mouse model of DM1.

a, Location of ASO targeting sequences relative to hACTA1 coding region and expanded CUG repeat in the 3′ UTR. b, Quantitative real-time RT-PCR of hACTA1-CUG^exp mRNA in quadriceps, gastrocnemius, and tibialis anterior (TA) muscle in HSA^LR mice treated with the indicated ASOs by subcutaneous injection of 25 mg/kg twice weekly for 4 weeks. Mice were anlayzed 1 week after the final dose (n = 4 per group). Shown are mean levels of transgene mRNA ± SD. ** P < 0.001, *** P < 0.0001 (1-way ANOVA). c, hACTA1-CUG^exp transcript levels in quadriceps are not affected by ASOs targeting unrelated transcripts (141923, randomer; 116847, Pten; 399462, Malat-1; n = 4 per group; same dose as b). Error bars ± SD. d, Knockdown of hACTA1-CUG^exp mRNA in muscle by ASO 190401 (n = 4 per group; same dose as b). Error bars ± SD. *** P ≤ 0.0005 (t-test). e, Northern analysis of RNA from quadriceps muscle. The level of CUG^exp RNA was determined using a (CAG)₉ oligonucleotide probe. Mouse actin serves as loading control. f, g, RT-PCR analysis of alternative splicing of Clcn1 (f) and Serca-1 (g) transcripts. For Clcn1, only the −ex7a isoform encodes a functional ion channel. −ex7a, exon 7a skipping; +ex7a, exon 7a inclusion; -ex22, exon 22 skipping; +ex22, exon 22 inclusion; wt, FVB/n wild-type; neg, negative control injected with GAC25 morpholino; pos, positive control injected with CAG25 morpholino. h, Blinded analysis of myotonia by electromyography, 1 week following final dose (n = 4 mice per group). Error bars ± SD. *** P < 0.0001 ASO- vs. saline-treated muscles (2-way ANOVA).