The R634W mutation we and others found in DCM patients (R636W in mouse), affecting the first arginine residue in the RSRSP stretch, diminished the function of RBM20 to an extent similar to that of the S635A mutation (S637A in mouse) in our splicing reporter assay (Fig. 6). The gene discussed is RBM20; the disease is familial dilated cardiomyopathy.