SCA-3 is a polyQ disorder caused by excessive CAG repeats leading to the expansion of a polyglutamine tract in ataxin-3, a protein identified in the study of the disease, whose normal function is related to many cellular functions, in particular to the control of ubiquitination/deubiquitination protein balance (Rüb et al., 2013). This evidence concerns the gene ATXN3 and Machado-Joseph disease.