The contribution of disease-associated dysregulation of alternative splicing to key symptoms is well characterized in the CTG repeat expansion disease, myotonic dystrophy type 1 (DM1).8 For example, missplicing of the CLCN1 chloride channel mRNA leads to inclusion of exon 7A, which contains a premature stop codon. The gene discussed is CLCN1; the disease is myotonic dystrophy type 1.