HDAC9 and Friedreich ataxia: Pathways related to epigenetic signaling, and synapse maturation, such as HDAC (Akhtar et al., 2009; Sada et al., 2020) and KDM1A (Ambrosio and Majello, 2018) were upregulated in FRDA; inhibitors of these genes have been explored for neurodegenerative diseases, including FRDA (Rai et al., 2010; Soragni et al., 2014; Polak et al., 2016; Soragni and Gottesfeld, 2016).