MBNL1 and myotonic dystrophy type 1: An RNA-binding protein, the muscleblind-like protein 1 (MBNL1), is sequestered to the CUG repeats6, 7, whereas another RNA-binding protein, the CUG-binding protein, Elav-like family member 1 (CELF1), is not sequestered but is activated in DM1 somehow by the abnormally expanded CUG repeats8.