CAP2 and cardiomyopathy: Because heart specific expression of Cre by some promoters can cause cardiomyopathy in the absence of floxed test genes37, 38, we performed survival controls on Myh6Cre-cap2+/cap2loxp (n = 41) mice and also on Myh6Cre-cap2+/cap2+ (n = 5) mice.