FXN and Friedreich ataxia: We have established a GAA repeat expansion mutation-based mouse model of FRDA, designated YG8R, by cross breeding YG8 human genomic YAC transgenic mice that contain the entire FXN gene and expanded GAA repeats (Al-Mahdawi et al., 2004) with heterozygous Fxn knockout mice (Cossee et al., 2000).