ATXN2 and amyotrophic lateral sclerosis: Because ALS might be treated by targeting nonmutant ATXN (5), we did not test HSP90 inhibitors in mice harboring CAG repeat–expanded ATXN2. We treated 27-week-old BAC ATXN2-Q22 mice with 17-DMAG (n = 4 per group; two males and two females) every other day over 16 days (days 1, 3, 5, 7, 9, 11, 13, and 15) and then sacrificed on day 16.