MYH14 and familial dilated cardiomyopathy: At the same time, the DCM-associated mutations significantly impaired the regulatory properties of cardiac Tpm by reducing the Ca2+ sensitivity of thin filaments determined by different methods, such as the measurements of Ca2+-dependence of actin-activated ATPase activity of myosin [14,16,23,26,27] and sliding velocity of reconstructed thin filaments in the in vitro motility assay [14,18,19,24].