DMPK and myotonic dystrophy type 1: DM is an RNA-dominant disorder caused by the expression of expanded CTG trinucleotide repeats located in the 3′ untranslated region (UTR) of the DM1 protein kinase (DMPK) gene in DM type 1 (DM1) [1] and by a tetra-nucleotide CCTG expansion in the zinc finger protein 9 (CNBP) gene in DM type 2 (DM2) [2].