Tissue-specific expression levels of Fxn, Tug1 and Slc40a1 in FRDAkd mice. (A) Fxn, (B) Slc40a1 and (C) Tug1, expression levels in heart, muscle, spinal cord, brain and liver tissues from FRDAkd mice treated with dox for 0 and 6 weeks (WK, Fxn knockdown), followed by an 8-week rescue period (Fxn recovery). Each time point included four samples (n = 4). (D) Linear regression models were employed to calculate R² values based on the log₂ fold-change of Tug1 and Slc40a1 expression levels, normalized to Hprt1, in the blood of FRDAkd mice during the Fxn knockdown and rescue phases. N = 3–5. Welch's t-test was used for statistical analysis. Data are presented as mean ± SEM, with significance marked as *P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001.