FXN and Friedreich ataxia: Given that the frataxin depletion causes ROS overload and iron-sulfur (Fe-S) cluster proteins impairment in FRDA (Lin et al., 2017b; Abeti et al., 2018; Lupoli et al., 2018), we measured the activity of mitochondrial (Fe-S) Complex I (CI) and ROS levels in KIKO NSCs, in order to validate our model.