FXN and Friedreich ataxia: Frataxin-depleted cells show abnormal FeS cluster formation, decreased activities of FeS cluster-containing proteins, iron accumulation in the mitochondrial matrix, increased reactive oxygen species (ROS) production, and impairment of the electron transport chain, leading to reduced ATP production (Lu and Cortopassi, 2007; Marmolino et al., 2010; Poburski et al., 2016) in FRDA patients and animal models.