Abstract
Splice-switching oligonucleotides (SSOs) have been used to modulate gene expression by interfering with pre-mRNA splicing with the intent to treat disease. For Duchenne muscular dystrophy, splicing modulation has been used to induce the skipping of exon 51 of the dystrophin transcript, allowing the production of a truncated but functional protein. Although oligonucleotide-based therapies are promising, the rapid degradation of oligonucleotides (ONs) by intracellular nucleases has been a major obstacle. Locked nucleic acid (LNA) substitution in SSOs protects oligonucleotides from nuclease degradation and enhances the hybridization properties of the oligo. However, the best optimum size of the oligo depends on the LNA substitution rate. Here we show that 16-mer DNA SSOs with 60% LNA substitution and full phosphorothioate (PS) linkage backbone efficiently induce exon 51 skipping in myogenic cells derived from a DMD patient, allowing expression of the dystrophin protein.