IRF9 and Friedreich ataxia: In support of these altered cytokine responses in FA cells, the cytokine-response genes myxovirus A (MxA), IFN response factor 1 (IRF1), p21CIP/WAF, and IFN-stimulated gene factor 3 (ISGF3γ) were highly expressed in FA mutant cells without exogenous cytokine stimulation, while corrected cells suppressed this overproduction and restored their MMC resistance [116, 131, 132].