FXN and Friedreich ataxia: We next applied an existing cohort of FRDA patient, unrelated control, and dual guide CRISPR/Cas9 FXN repeat gene edited iPSCs8, and generated additional asymptomatic familial carrier cell lines heterozygous for the GAA FXN repeat expansion as immediate familial controls of FRDA patients within this cohort (Fig. 1c and Supplementary Fig. 1b-e).