Disrupted functions of MBNL proteins, in particular MBNL1 and MBNL2, are associated with DM disease, caused by CUG expansions in the 3′-untranslated region (3′-UTR) of dystrophia myotonica protein kinase gene (DMPK) for DM1 or by CCUG expansions in the first intron of cellular nucleic acid-binding protein gene (CNBP or ZNF9) for DM2. This evidence concerns the gene DMPK and myotonic dystrophy type 1.