FXN and Friedreich ataxia: We then investigated whether the differential sensitivity to UVA observed in the human fibroblasts also held true in cells derived from a mouse model of FRDA.42 In this model, FRDA mouse (YG8sR) carries the FXN transgene from an FRDA patient, and thus expresses low levels of FXN compared to control mouse (Y47R) which expresses the FXN transgene from an unaffected donor.