The number of repeats in the mutant ATXN3 allele ranges from 52 to 91 in SCA3/MJD patients, which results in the expansion of a polyglutamine tract within the ATXN3 protein (Todd and Paulson, 2010; Souza et al., 2016). Here, ATXN3 is linked to Spinocerebellar ataxia type 3.