DMPK and myotonic dystrophy type 1: On the other hand, a transgenic mouse expressing a human skeletal actin fragment with a 3′UTR (CTG)>250, mimicking the location of the repeat expansion in DMPK, in a muscle-specific gene, developed limb difficulties, myotonia and myopathy, indicating that the expanded (CUG)n RNA is sufficient to cause DM1 clinical features in muscle [176].