In contrast to some of the MJD transgenic mice expressing full-length ataxin-3 developed in the last years [30]–[36], whose behavioral and neuropathological deficits are mild and develop after several months of age, the use of a truncated form of ataxin-3 leads to an early and severe MJD phenotype with robust abnormal neuropathological and behavior deficits while maintaining physiological relevance for this particular question [15], [37]. This evidence concerns the gene ATXN3 and Machado-Joseph disease.