SUMOylation was also deregulated in the R6/2 mouse model of HD: both Sumo1 and Sumo2 mRNA increased in the striatum at a late stage of the disease; the same pattern was observed in the mRNA expression of enzymes (Senp1, Senp6, Pias3 and Pias4) involved in this pathway (O'Rourke et al., 2013). This evidence concerns the gene PIAS4 and Huntington disease.