FXN and Friedreich ataxia: The YG8R mice exhibit an FRDA-like molecular disease phenotype that includes intergenerational and somatic instability of the GAA repeat expansion mutation (Al-Mahdawi et al., 2004; Clark et al., 2007), together with increased DNA methylation, reduced histone H3 and H4 acetylation and increased di- and trimethylated H3K9 at the FXN upstream GAA region, when compared with Y47R control transgenic mice that contain the same human FXN YAC transgene but with normal-sized GAA repeats (Al-Mahdawi et al., 2008).