It has been suggested that CUGBP1 and MBNL1 cause DM1 pathology through the binding to two different forms of mutant CUG RNA: “insoluble” or aggregated CUG repeats (MBNL1) and “soluble” or un-aggregated CUG RNA (CUGBP1) (Fig. 4). This evidence concerns the gene CELF1 and myotonic dystrophy type 1.