BNANC Gapmers Revert Splicing and Reduce RNA Foci with Low Toxicity in Myotonic Dystrophy Cells.

Myotonic dystrophy type 1 (DM1) is a multisystemic disease caused by an expanded CTG repeat in the 3' UTR of the dystrophia myotonica protein kinase (DMPK) gene. Short, DNA-based antisense oligonucleotides termed gapmers are a promising strategy to degrade toxic CUG expanded repeat (CUGexp) RNA. Nucleoside analogs are incorporated to increase gapmer affinity and stability; however, some analogs also exhibit toxicity. In this study, we demonstrate that the 2',4'-BNANC[NMe] (BNANC) modification is a promising nucleoside analog with high potency similar to 2',4'-LNA (LNA). BNANC gapmers targeting a nonrepetitive region of the DMPK 3' UTR show allele-specific knockdown of CUGexp RNA and revert characteristic DM1 molecular defects including mis-splicing and accumulation of RNA foci. Notably, the BNANC gapmers tested in this study did not induce caspase activation, in contrast to a sequence matched LNA gapmer. This study indicates that BNANC gapmers warrant further study as a promising RNA targeting therapeutic.