ROS is suggested to contribute to the accumulation of insoluble proteinaceous deposits, such as Lewy bodies in PD, and senile plaques and NFT in AD [23–25], and dysfunction of complex I in the oxidative phosphorylation (OXPHOS) system has been shown to accelerate 4R tau isoform formation in PSP cell lines [26] and is defective in the substantia nigra of PD patients [27, 28]. The gene discussed is MAPT; the disease is Parkinson disease.