Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder caused by deletions in the DMD gene, resulting in the absence of functional dystrophin and progressive muscle degeneration. Previous research highlighted that DMD patients missing exon 49 exhibited improved muscular phenotypes compared to those with other DMD mutations (Abaji, M. et al., Genes 2022). Herein, the investigators performed an in vitro experiment to demonstrate the feasibility of skipping exon 49 in human myotubes.
The purpose of our study was to: 1) elucidate an exon analogous to exon 49 on the dys-1 gene of the BZ33 strain—a Caenorhabditis elegans (C. elegans) model of DMD with severe locomotory defects; and 2) design an antisense oligonucleotide (ASO) to facilitate the skipping of the analogous exon, rescuing the models’ phenotype. Analysis of the dys-1 gene identified exon 42 as analogous to exon 49 in patients due to its shared nonsense mutation. The ASO was designed based on the complementary sequence to a string of 20 nucleotides between exon 42 and its preceding intron and was administered via soaking the models in a solution containing the ASO. After two days of soaking, locomotion was evaluated through a swim test, comparing wildtype (N2), untreated BZ33, ASO-treated BZ33 (BZ33+SG1), and vehicle-treated BZ33 (BZ33+Vehicle) nematodes. Swim test was assessed by determining the number of body bends, defined as a period of one sinusoidal movement, and/or twitches, sporadic or abnormal movements that deviated from the sinusoidal track, during one-minute intervals. The results showed notable improvement in locomotion for BZ33+SG1 nematodes, with a median of 38 body bends per minute compared to 0.5 and 1 body bend per minute for untreated and vehicle-treated BZ33 strains, respectively. These findings indicate that ASO-mediated exon skipping effectively restores functional dystrophin analogs in C. elegans. The results warrant further investigation in determining if the skipping of exons analogous to exon 42 improves locomotory function in relevant rodent and non-human primate models.