Caudate-putamen (CP) and total hemispheric atrophy were observed in adult zQ175Δneo mice compared to WT littermates. (A,B) Representative images of H&E-stained coronal brain sections from 57-week-old female WT and zQ175Δneo mice at (A) +0.8 mm and (B) −1.80 mm distance from bregma. Dashed lines indicate the measured area of (A) CP and (B) total hemisphere. The scale bars indicate 1000 µm. (C–F) Male (C,E) and female (D,F) zQ175Δneo mice (●) show a reduction of the CP area (C,D) and the total hemisphere (E,F) compared to WT littermates (○). Data are presented as mean ± SD; N = 2–6. Significance was calculated using unpaired t-test followed by Holm-Šídák correction and is given as *: p ≤ 0.05, and **: p ≤ 0.01.