FXN and Friedreich ataxia: In this regard, it has been observed that the exogenous expression of recombinant Nqo15 in FRDA patients’ cells is able to ameliorate the respiratory phenotype [40]; the extent of this effect is comparable to what is observed by re-expressing FXN in these cells, indirectly supporting the hypothesis that FXN could play a key role in mitochondrial complex I proteostasis.