Treatment of DM1 cells with antisense oligonucleotides. Cells were transfected with 1 μg of oligonucleotides (AON) targeting the CUG triplet repeat, and RNA foci visualized using FISH with a Cy3-labeled CAG probe (red dots). (C and D) Differentiated DM1 cells cultivated in HS medium, 2 weeks post-myoD-transduction. (A and B) DM1 fibroblasts. (B and D) Cells transfected with AONs. (A and C) Untransfected. Original magnification × 630.