fig3

Figure 3. Progressive degeneration of DA neurons in the midbrain of G59S Tg and G71R Tg mice. (A) Immunohistochemical images show TH staining in the coronal midbrain sections of 24-month-old nTg, WT Tg, G59S Tg, and G71R Tg mice. Scale bar: (left) 500 μm (low-magnification images) and (right) 50 μm (high-magnification images). Note the dystrophic TH-positive DA neurites in the SNr of G59S Tg and G71R Tg mice. (B) Bar graphs depict the unbiased stereological estimation of the number of TH-positive DA neurons in the SNc of 24-month-old nTg, tTA, tetO-WT, WT Tg, tetO-G59S, G59S Tg, tetO-G71R, and G71R Tg mice (n = 4 per genotype). Data are presented as mean ± SEM. One-way ANOVA with Dunnett’s multiple comparisons test was used for statistical analysis (the mean of each genotype was compared with the mean of nTg). ^****P < 0.0001. ns: Not significant. (C) Bar graphs depict the unbiased stereological estimation of the number of TH-positive DA neurons in the SNc of 1-, 6-, and 12-month-old nTg, WT Tg, G59S Tg, and G71R Tg mice (n = 4 per genotype per time point). Data are presented as mean ± SEM. At each time point, one-way ANOVA with Dunnett’s multiple comparisons test was used for statistical analysis (the mean of each genotype was compared with the mean of nTg). ^**P = 0.0099, ^***P = 0.0001. (D) Bar graphs depict the unbiased stereological estimation of the number of TH-positive DA neurons in the VTA of 24-month-old nTg, WT Tg, G59S Tg, and G71R Tg mice (n = 4 per genotype). Data are presented as mean ± SEM. One-way ANOVA with Dunnett’s multiple comparisons test was used for statistical analysis (the mean of each genotype was compared with the mean of nTg). ^****P < 0.0001. (E) Bar graphs quantify the area percentage of dystrophic TH-positive DA neurites in the SNr of 2- and 24-month-old nTg, WT Tg, G59S Tg, and G71R Tg mice (at each time point, n = 4 animals per genotype and 5 sections per animal). Dystrophic DA neurites were defined as neuritic varicosity ≥ 25 μm². Data are presented as mean ± SEM. At each time point, one-way ANOVA with Dunnett’s multiple comparisons test was used for statistical analysis (the mean of each genotype was compared with the mean of nTg). ^*P = 0.0259, ^****P < 0.0001. TH: Tyrosine hydroxylase.