MFN1 and cardiomyopathy: Furthermore, transgenic mice (loxP/Myh6-Cre) deficient in cardiac-specific MFN1 and MFN2 from the late embryonic period displayed severe mitochondrial dysfunction at 7 days (abnormal mitochondrial structure, down-regulated mitochondrial biogenesis genes, reduced mitochondrial DNA), developed cardiomyopathy, and all died before 14 days old (Papanicolaou, Kikuchi, et al., 2012).