Reprogramming activates the FA pathway and induces DNA damage. (A) Representative photomicrograph of FANCD2 immunofluorescence in control transduced or reprogrammed WT TTFs (60× magnification). (B) Percentage of cells containing FANCD2 foci as assessed by immunofluorescence 7 days after reprogramming. (C) Normalized expression of p53, p21, and p19 as determined by immunoblot in WT and Fanca^−/− TTFs at baseline and 4 days after reprogramming (n = 4). Data are ± SEM. (D) Level of ROS measured by 2′,7′-di-chlorofluorescein (DCF) FACS analysis at baseline and 2 days after reprogramming. (E-F) Percentage of cells with ≥ 5 γH2AX foci (E) and percentage of cells undergoing senescence at baseline and 4 days after reprogramming (F). Filled circles, WT; open circles, Fanca^−/−. OSKM indicates Oct3/4, Sox2, Klf4, c-Myc. *P < .05; **P < .01; NS, not significant by Wilcoxon rank-sum test. Horizontal line in panels B, D, E, and F represents the median.