Further, these data suggest that up-regulation of MAPK signaling by mutant RIT1 may drive the dysregulation of cardiomyopathy-associated genes, such as Mybpc3 (myosin-binding protein C), a causal gene representing approximately 20% of patients with HCM (40), and Actc1 (cardiac α-actin), among others (fig. The gene discussed is ACTC1; the disease is cardiomyopathy.