The observation that inhibition of NHEJ exacerbated genomic instability in Fanca−/− HSPCs appears to be conflict with previous reports that inhibition of the key NHEJ factors such as Ku, Lig4, or DNA-PKcs could ameliorate the sensitivity of FA cells to interstrand crosslinking agents [12, 15]. This evidence concerns the gene LIG4 and Friedreich ataxia.