OMA1 and hydrops fetalis: Reduced Opa1 expression and small mitochondrial fragmentation appear in the failing hearts, indicating decreased mitochondria fusion in the failing hearts.222 In mice, specific deletion of Yme1l in the heart activates OMA1, leads to increased Opa1 degradation, fragmented mitochondria, and altered metabolism of the heart, finally, resulting in dilated cardiomyopathy and HF.223 However, deletion of Oma1 prevents cleavage of Opa1, which in turn rescues cardiac function and mitochondrial morphology.