The finding that MBNL knockout mice and CUG-BP1 overexpressing transgenic mice can recapitulate most DM1 phenotypic features, in the absence of expanded CUG-repeats, and henceforth foci, suggests that foci per se are not required for DM1 pathogenesis (21,29,73,74). The gene discussed is MBNL1; the disease is myotonic dystrophy type 1.