While the exact correlation between disruption of the mitochondrial network and mitochondrial function and biogenesis is still a matter of debate in the case of HD (reviewed in Costa and Scorrano, 2012), complex-II impairment emerges as key event of mitochondrial dysfunction in SCA3 and has been observed in different SCA3 cell and animal models as well as in peripheral cells of SCA3 patients (Laço et al., 2012). Here, ATXN3 is linked to Machado-Joseph disease.