Fig. 6
Three copies of Cstb increase cystatin B (CSTB) in the cortex of mouse models of AD-DS but do not alter cathepsin B activity. a, b CSTB protein abundance (determined by western blot) was measured in cortex of a 3-month old mouse model of AD-DS (progeny from a cross of Dp(10)2Yey and AppNL−F/NL−F), including in Dp(10)2Yey and Dp(10)2Yey; AppNL−F/NL−F genotypes which have three copies of Cstb. The abundance of CSTB was significantly increased by the Dp(10)2Yey region (ANOVA F(1,22) = 31.269, p < 0.0001). Significantly higher CSTB levels were detected in Dp(10)2Yey compared to wildtype (WT) (pairwise comparisons with Bonferroni correction, p < 0.001) and AppNL−F/NL−F (pairwise comparisons with Bonferroni correction, p = 0.003) cortex. Significantly higher CSTB levels were detected in Dp(10)2Yey; AppNL−F/NL−F cortex compared to wildtype (WT) (pairwise comparisons with Bonferroni correction, p = 0.005) and AppNL−F/NL−F (pairwise comparisons with Bonferroni correction, p = 0.015) cortex. c–h Cathepsin B activity determined by biochemical assay (rate of cleavage of Ac-RR-AFC, corrected for non-specific activity measured in samples inhibited by c, e, g, i ALLM or d, f, h, j FMK(z-FA-FMK). c, d No difference in cathepsin B activity was detected in cortex of 3-month old mice carrying the Dp(10)2Yey segmental duplication compared to animals without the duplication including WT and AppNL−F/NL−F genotypes (progeny from a cross of Dp(10)2Yey and AppNL−F/NL−F mice); c ALLM (ANOVA F(1,22) = 1.325 p = 0.262) or d FMK (ANOVA F(1,22) = 1.142 or p = 0.297). No difference in cathepsin B activity was detected in cortex from 3-month-old mice homozygous for the AppNL−F allele that results in amyloid-β accumulation (AppNL−F/NL−F and Dp(10)2Yey; AppNL−F/NL−F genotypes); c ALLM (ANOVA F(1,22) = 0.571 p = 0.458) or d FMK (ANOVA F(1,22) = 0.815 or p = 0.376). e No difference in cathepsin B activity was detected in cortex of 3-month old mice with the Dp(10)2Yey segmental duplication (generated from a cross to C57BL/6J) ALLM (ANOVA F(1,10) = p = 0.118). f A modest reduction in cathepsin B activity was detected in cortex of 3-month old mice with the Dp(10)2Yey segmental duplication (generated from a cross to C57BL/6J) FMK (ANOVA F(1,15) = 5.542 p = 0.033). No difference in cathepsin B activity was detected in cortex of 3-month-old mice with the Dp1Tyb segmental duplication (generated from a cross to C57BL/6J), g ALLM (ANOVA F(1,24) = 0.010 p = 0.923) or h FMK (ANOVA F(1,18) = 0.013 or p = 0.909). i, j No difference in cathepsin B activity was detected in cortex of 3-month old mice with the Dp(17)3Yey segmental duplication (generated from a cross to C57BL/6J), i ALLM (ANOVA F(1,12) = 0.543 p = 0.475) or j FMK (ANOVA F(1,12) = 0.731 or p = 0.409). Individual data points are technical means for independent biological samples, error bars SEM. *p < 0.05, **p < 0.01, ***p < 0.001. Male and female mice were used and sex was included as a variable in the ANOVA, cohort details Table 3