These mechanisms have been described to be impacted by PolyQ protein expression: for example, chaperones and/or proteasome components have been detected in protein aggregates associated with HD, SCA1, SCA3 and SBMA, in cell models101–103, animal models104,105 and patient brain samples106,107; autophagy has been described to be impaired in animal models of SCA1 and SBMA (refs.108,109), and in patients of HD, SCA3, SCA7 (refs. 110,111,112). This evidence concerns the gene AR and Huntington disease.