C9orf72 and Spinocerebellar ataxia type 3: To assess whether sense strand–derived KGREG peptide products accumulate in brains of patients with CANVAS, we performed immunohistochemistry on CANVAS (n = 4) as well as control [n = 16, including disease controls from cases of spinocerebellar ataxia type 3 (n = 1), C9orf72-associated FTD/ALS (n = 2), Huntington’s disease (n = 2), and 11 nondisease controls] postmortem brain samples obtained from the University of Michigan Brain Bank, MassGeneral Brigham SCiN, Queen Square Brain Bank UCL, and the Netherlands Brain Bank (Fig. 2F, fig.