XRCC3 and Friedreich ataxia: Regarding the other DNA repair pathways, we analyzed DNA repair-related gene expression in FACS-sorted tubular epithelia; parp1, parp2, xrcc1 and aptx for SSB repair, xrcc2 and xrcc3 for homologous recombination (HR), and fancd2 and bcra2 for the Fanconi anemia (FA) pathway (Fig. 6e).