This in turn produces a complex array of clinical findings in which specific endophenotypes, such as myotonia, heart block, or insulin resistance, are linked to splicing defects of particular genes, such as CLCN1 (chloride channel) (2–4), SCN5A (sodium channel) (5, 6), or INSR (insulin receptor) (7). Here, CLCN1 is linked to Myotonia.