MT-CYB and Parkinson disease: This was validated using cytochrome b mutant cybrids, generated by reconstituting 143B ρ0 cells with wild-type mitochondrial DNA or that containing a 4-bp deletion in the cytochrome b gene found in a patient suffering from parkinsonism (loss of cytochrome b renders these cells incapable of O2 consumption and unable to generate ROS at the Qi site specifically).