To determine whether FAAP100 is the gene responsible for the cellular phenotype observed in patient-derived cells, FAAP100fs/fs fibroblasts were complemented with WT N-terminally HA-FLAG tagged FAAP100 cDNA, FAAP100fs cDNA, or vector control and were assayed for rescue of the FA phenotype. The gene discussed is FAAP100; the disease is Friedreich ataxia.