FXN and Friedreich ataxia: Usdin and colleagues then reported increased H3K9me2 levels within FXN intron 1 in FRDA lymphoblastoid cells (Greene et al., 2007) and our laboratory reported changes of histone modifications at the FXN promoter, upstream, and downstream GAA repeat regions in FRDA patient and YAC transgenic mouse brain tissues (Al-Mahdawi et al., 2008).