DNAH8 and familial dilated cardiomyopathy: Although previous investigations have been inconsistent, in vitro studies have suggested that HCM mutations in several genes lead to an increase in Ca2+ sensitivity, increases in tension generation, and/or increases in ATPase activity [7]–[12], whereas DCM mutations are associated with Ca2+ desensitization and/or decreased ATPase activity in vitro or in permeabilized rabbit cardiac muscle fibers and isolated myocytes [13]–[18].