Notably, polyQ-expanded ATXN7 reduces SAGA deubiquitinase activity in vivo; thus, defects in ubH2B deubiquitination could induce the retinal degeneration that is unique to this ataxia (McCullough et al. 2012; Yang et al. 2015; Lan et al. 2015). This evidence concerns the gene ATXN7 and cerebellar ataxia.