Specifically, in HD and/or DM1 mice, TNR instability is reduced upon inactivation of genes involved in mismatch repair (MMR), including Msh2, Msh3 and Pms2 [30,31,32,33,34], base excision repair (BER), including Ogg1 and Neil1 [35,36], and nucleotide excision repair (NER), including Xpa and Csb [37,38]. The gene discussed is PMS2; the disease is Huntington disease.