CELF1 and myotonic dystrophy type 1: Western blot analysis of cytoplasmic extracts from transfected normal and DM1 myoblasts and fibroblasts show that the total cytoplasmic levels of CUGBP1 are increased in DM1 myoblasts and fibroblasts, and are not affected significantly by SMAUG1 (Figure 6A–6B and Figure S5).