To investigate FRDA molecular disease mechanisms and therapy, we have previously established three human FXN YAC transgenic mouse models: Y47R, containing normal-sized (GAA)9 repeats, and YG8R and YG22R, which initially contained expanded GAA repeats of 90–190 units and 190 units, respectively, but which have subsequently been bred to now contain expanded GAA repeats of 120–220 units and 170–260 units, respectively [7]. This evidence concerns the gene FXN and Friedreich ataxia.