CELF1 and myotonic dystrophy type 1: In DM1, the most studied families of RNA-binding proteins (RBPs) affected by mutant DMPK transcript toxicity are the CUGBP-ETR-3-like (CELF) and Muscleblind-like (MBNL) factors, both controlling the inclusion of alternative exons in several transcripts according to tissue and developmental state cues [10].