A Selective Alkylating Agent for CTG Repeats in Myotonic DystrophyType 1

Disease intervention at the DNA level generally hasbeen avoided because of off-target effects. Recent advances ingenome editing technologies using CRISPR-Cas9 have opened anew era in DNA-targeted therapeutic approaches. However,delivery of such systems remains a major challenge. Here, wereport a selective DNA-modifying small molecule that targets adisease-specific structure and mismatches involved in myotonicdystrophy type 1 (DM1). This ligand alkylates T-T mismatch-containing hairpins formedin the expanded CTG repeats(d(CTG)exp) in DM1. Ligand alkylation of d(CTG)expinhibitsthe transcription of d(CAGmiddotCTG)exp, thereby reducing the level ofthe toxic r(CUG)exptranscript. The bioactivity of the ligand also included a reduction in DM1 pathological features such as diseasefoci formation and misregulation of pre-mRNA splicing in DM1 model cells. Furthermore, the CTG-alkylating ligand may changethe d(CAGmiddotCTG)exprepeat length dynamics in DM1 patient cells. Our strategy of linking an alkylating moiety to a DNA mismatch-selective small molecule may be generally applicable to other repeat expansion diseases such as Huntington's disease andamyotrophic lateral sclerosis