MBNL1 and Myotonia: Notably, Mbnl1−/−; ClC-1ΔE7a muscle displayed a significantly reduced percent of fibers with central nuclei (~56% less) as compared to Mbnl1−/− samples (p = 0.0004, Fig. 5b), which indicates that myotonia may play a role in driving central nucleation in DM1 mice.