A POINT MUTATION IN THE CYTB GENE OF CARDIAC MTDNA ASSOCIATED WITH COMPLEX-III DEFICIENCY IN ISCHEMIC CARDIOMYOPATHY

We report a high incidence of reduced respiratory Complex III activity in heart muscle concomitant with the presence of a specific mutation in cytochrome b (cytb) in patients with ischemic cardiomyopathy. This C --> A mutation at nt 15452 converts the 236th residue of cytb from a leucine to isoleucine, is heteroplasmic and was observed in only 2 of 43 controls. Complex III activity is reduced (>50%) in 5 of 6 patient s with the C --> A(15452) mutation suggesting that the cytb mutation i s responsible for decreased Complex III activity and may play a role i n the pathophysiology of ischemic cardiomyopathy.