A recent study demonstrated region-specific changes in the abundance of ubiquitinated proteins in MJD mice, with expression of polyQ-expanded ataxin-3 resulting in significantly increased abundance of K63-ubiquitinated proteins in the cerebellum and brainstem, and decreased abundance of K48-ubiquitinated proteins in the brainstem of 7-week-old MJD mice [100]. The gene discussed is ATXN3; the disease is Machado-Joseph disease.