In a postmortem study of PD patients, it was even shown that levels of the nuclear factor erythroid 2-related factor 1 (Nrf1), also known as nuclear factor erythroid-2-like 1 (NFE2L1), a protein involved in the regulation of mitochondrial function, were drastically reduced or even absent [56]. This evidence concerns the gene NFE2L1 and Parkinson disease.