Analysis of the dynamic behaviour of MBNL1 and CUGBP1 in live cells further implicates CUGexp RNA and MBNL1 as regulators of the formation and turnover of cytoplasmic SGs, suggesting a mechanism by which the presence of CUGexp RNA and disruption of the subcellular distribution of MBNL1 results in deregulation of SGs and, by extension, the fine control of cytoplasmic RNA metabolism in DM1. Here, MBNL1 is linked to myotonic dystrophy type 1.