Iron dysregulation in FRDA fibroblasts. (A) Immunoblot of frataxin in fibroblasts of 5 FRDA patients (P1-P5) and 3 controls (C1-C3) grown in regular medium. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a loading control. (B) Iron quantification using the ferrozine-based colorimetric assay in subcellular fractions of control (C* indicates mean of 3 controls) and FRDA (P1-P5) cells grown in regular medium. (C) Relative cytosolic and mitochondrial iron content in controls (C*) and FRDA cells (P1-P5). (D) Immunoblot of several proteins involved in iron homeostasis, ROS defense, and mitochondrial function in control (C1-C3) and FRDA (P1-P5) fibroblasts grown in regular medium. GAPDH was used as a loading control. (E) Quantification of mitochondrial ROS using MitoSOX Red and flow cytometry for control (C*) and FRDA (P1-P5) fibroblasts in regular medium. Data expressed as percentages of MitoSOX⁺ cells relative to control value. All bar plots show mean ± standard error (n = 3). Student t tests were used to compare patients’ values with control mean. Immunoblotting quantifications are presented in supplemental Figure 1. *P < .05, **P < .01, ***P < .001. ns, nonsignificant.