FXN and Friedreich ataxia: The YG8R mouse model of FRDA – FXN-knockout mice that are also hemizygous for the YG8 transgene (which carries two tandem copies of the human FXN gene with two GAA trinucleotide repeat expansions) – has been used to successfully test the safety and efficacy of frataxin-increasing drug compounds, such as histone deacetylase inhibitors and interferon-γ.