Several studies using cellular and animal models of MJD, including the YACMJDQ84.2 (Q84) transgenic mice that are frequently used in pre-clinical studies of MJD [10,11,12,13,14], have been revealing that mutant ATXN3 harboring an expanded polyQ tract is involved in the impairment of transcription, mitochondrial function, mechanisms regulating oxidative stress, and apoptosis [3,15,16]. Here, ATXN3 is linked to Machado-Joseph disease.