Colocalization of Ku70 and mutant Htt in the nucleus. (A) Immunocytochemical detection of colocalization of Ku70 and mutant Htt in cultured neurons at 4 d after mutant Htt infection (arrows). Endogenous Ku70 (red) colocalized with mutant Htt inclusion (green) in cultured neurons infected by AXCA-Htt111Q. Bars, 5 µm. (B) Immunohistochemical analysis showing colocalization of endogenous Ku70 (red) and mutant Htt (green) in striatal neurons of R6/2 mice (arrowheads) and age-matched nontransgenic littermates (wild type [wt]) at 12 wk. Bar, 25 µm. (C) High power magnification of striatal neurons of R6/2 mice and nontransgenic littermates (wild type) at 12 wk. Top and middle show ordinary and confocal microscopic images, respectively. (bottom) Graphs show quantitative analyses of signal intensities acquired from confocal images along the arrow line, showing that Ku70 and mutant Htt are colocalized. Bars, 5 µm. (D) γH2AX is not colocalized with Ku70. IR, wild-type mouse brain irradiated with 20 Gy. Bar, 5 µm.