Because co-localization of MBNL1 with CUGexp ribonuclear inclusions is thought to lead to functional impairment of nuclear MBNL1 activity in DM1, we tested the hypothesis that RNA gain-of-function effects in SCA8 contribute to the motor deficits in SCA8 BAC-EXP mice via Mbnl1 depletion. This evidence concerns the gene ATXN8OS and myotonic dystrophy type 1.