Sequestration of the splicing factor MBNL1 by the RNA foci, which leads to splicing disruption of MBNL1 target genes, is the main molecular feature associated with DM1 skeletal muscle pathology (Meola and Cardani, 2015; Tang et al., 2012; Fugier et al., 2011). The gene discussed is MBNL1; the disease is myotonic dystrophy type 1.