Although the siRNA-mediated knockdown of the targets we identify provides evidence of the importance of H4K20 methylation in the regulation of expression of FXN, histone lysine methylation and histone arginine methylation have not been extensively studied in FRDA, despite the fact that several reports describe histone methylation marks in the GAA expanded region (17). The gene discussed is FXN; the disease is Friedreich ataxia.