TNNT2 and familial dilated cardiomyopathy: Initial immunocytochemical analysis for titin and various proteins marking different portions of the sarcomere—α-actinin (Z-disk), cardiac troponin T (cTNT, A-band), and myosin heavy chain (MHC, M-line)—revealed, in the DCM group, a higher percentage of cardiomyocytes in which organized myofibrils occupied only half of the whole cytoplasm or less (Fig3B).