MBNL1 and neuromuscular disease caused by qualitative or quantitative defects of dystrophin: While PE usage is implicated in dystrophinopathies, the pathophysiology of both myotonic dystrophy type 1 (DM1) and type 2 (DM2) is also associated with the sequestration of Muscleblind-like (MBNL) proteins to RNAs containing CUG or CCUG repeats (Sznajder and Swanson, 2019).