MBNL1 and myotonic dystrophy type 1: In contrast, expression of a high number of copies of the DMPK 3’ UTR containing 5 CUG repeats leads to development of DM1-like phenotype (myotonia, cardiac conduction defects and muscular dystrophy) in the absence of nuclear CUG foci and in the absence of MBNL1 sequestration [34].