Figure 4. CSF mHTT levels are dynamic following mHTT lowering restricted to the striatum.

A) Graphical experimental overview where 4 month old BACHD animals received bilateral IS injections of either PBS or 0.5μg of HTT ASO. Animals were collected at 2, 4, 8 and 12 weeks post-injection and mHTT levels in the brain and CSF were quantified. B) Representative western blots and C) relative quantification of mHTT in the CTX, STR, HIP and CBL at different timepoints following bilateral IS injections with either PBS or 0.5μg HTT ASO (N=6–14 for PBS, N=4–6 for 0.5 μg HTT ASO - 2 weeks, N=5–14 for 0.5 μg HTT ASO - 4 weeks, N=12 for 0.5 μg HTT ASO - 8 weeks, N=6 for 0.5 μg HTT ASO - 12 weeks. Two-way ANOVA: treatment p<0.0001, timepoint p<0.0001, interaction p<0.0001. Tukey’s multiple comparison test: compared to PBS **p=0.0094, ****p<0.0001). D) Relative quantification of mHTT levels in the CSF normalized to the mean of 2 week PBS mHTT MFI shows that CSF mHTT levels are dynamic following selective reduction of mHTT in the STR (N=3–11 for PBS, N=3–5 for 0.5 μg HTT ASO per timepoint. Two-way ANOVA: treatment p=0.0004, timepoint p=0.1714, interaction p=0.9723. Sidak’s multiple comparison test: 2 weeks p=0.3285, 4 weeks p=0.2252, 8 weeks p=0.1623 and 12 weeks p=0.1561 0.5μg HTT ASO compared to PBS; Test for linear trend: PBS p=0.1171, HTT ASO p=0.0855). E) Comparison of STR mHTT and CSF mHTT levels in matched samples at all timepoints following bilateral IS injections with either PBS or 0.5μg HTT ASO shows a significant correlation between these variables (Linear regression: R²=0.2135, p=0.0040). IS = intrastriatal, CTX = cortex, STR = striatum, HIP = hippocampus, CBL = cerebellum, CSF = cerebrospinal fluid, IOD = integrated optical density, MFI = median fluorescence intensity.