CRISPR/Cas9-mediated genomic deletions of trinucleotide repeats in Myotonic Dystrophy type 1: a new tool for gene therapy?

Myotonic dystrophy type 1 (DM1) is the most common adult-onset muscular dystrophy, caused bya (CTG)n expansion within the 3' untranslated region of the DMPK gene and characterised byprogressive myopathy, myotonia and multiorgan involvement. Expression of the mutated generesults in production of toxic transcripts that aggregate as nuclear foci where RNA-binding proteinsare sequestered, resulting in mis-splicing of several transcripts, defective translation and microRNAdysregulation. No effective therapy is yet available for treatment of the disease. In this study weexploited the CRISPR/Cas9 gene editing strategy to remove the pathogenetic repeat expansions forfuture therapeutic use. To this aim we generated DM1 myogenic cell models from DM1 patientderivedfibroblasts, exhibiting typical disease-associated alterations. We will show that by using theCRISPR/Cas9 and NHEJ gene-editing system CTG expansions can be removed permanently fromDMPK gene, resulting in phenotypic reversion of edited cells.