CELF1 and myotonic dystrophy type 1: We thank Dr. Charles Thornton (University of Rochester, NY) for kindly providing us with anti-MBNL1 rabbit polyclonal antibodies, DM1 human and HSALR mouse tissues; Dr. David Brook (University of Nottingham, UK) for pEGFP-MBNL1, pEGFP-hnRNP-C, pEGFP-CUGBP1 and DM1 fibroblasts with BpmI polymorphism; Dr. Scott Vande Pol (University of Virginia, VA) for pEGFP empty vector and the HEK293T cell line and Dr. I. H. Engels (Genomics Institute of the Novartis Research Foundation, CA) for immortalized DM1 fibroblasts/myoblasts.