In this project, the investigators are using iPSC lines derived from patients with Leigh syndrome that carry mutations in the mitochondrial (mtDNA) and in the nuclear DNA (nDNA) to reprogram them into neural progenitor cells and into dopaminergic neurons. The researchers are using this experimental system to screen FDA (Food and Drug Administration, USA) and EMA (European Medicines Agency) approved drugs for a positive effect on Leigh patient-derived neuronal cells (drug repurposing) using various biochemical, optic, and morphological outcome measures. Confirmed positive hits may be used for compassionate off-label use in Leigh patients when no standard treatment is available.