MBNL1 and myotonic dystrophy type 1: RNA dominant effects in DM1 have been hypothesized to stem in part from the ability of CUGexp to aberrantly sequester and functionally inactivate members of the muscleblind (MBNL) family of proteins10, 11, 12, increase steady-state levels of CUG-BP1 and other RNA binding proteins and from the nuclear exclusion of SHARP8, 21, 22.