The complex I inhibition hypothesis was further supported by the finding of reduced complex I activity in various tissues from Parkinson’s disease patients, including familial forms of Parkinson’s disease with the loss-of-function mutation of PTEN-induced putative kinase 1 (PINK1)7, 8, 9, 10, 11, 12, 13, 14. The gene discussed is PINK1; the disease is Parkinson disease.