CYCS and Parkinson disease: Interestingly, expression of wild type (WT) CHCHD2 in CG5010 knockout cells suppresses cytochrome c release and therefore downstream caspase activation, while the PD-associated CHCHD2 T61I or R145Q mutants do not (Meng et al., 2017), indicating that T61I and R145Q are at least partial loss-of-function mutations in Drosophila. In PD patient fibroblasts harboring the homozygous CHCHD2 A71P mutation, CHCHD2 levels are significantly decreased along with subunits of complexes I, IV, and V, resulting in impaired respiratory rates of complex I and IV (Lee et al., 2018).