Figure 3. Axonal but not dendritic transport of APP depends on HTT phosphorylation.

(A) Kymographs and quantifications of APP-mCherry into WT, HTT_SA and HTT_SD axons. Velocity, vesicle number per 100 µm of neurite length, cumulative distance and directional net flux were measured. Histograms represent means +/- SEM of 3 independent experiments, 41 WT, 52 HTT_SA and 63 HTT_SD axons and 674 WT, 602 HTT_SA and 493 HTT_SD vesicles. Significance was determined using an unpaired t-test; *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, ns = not significant. Scale bar = 20 µm. (B) Kymographs and quantifications of APP-mCherry into WT, HTT_SA and HTT_SD dendrites. Dendritic inward and outward velocity, vesicle number per 100 µm of neurite length, cumulative distance and directional net flux were measured. Histograms represent means +/- SEM of 4 independent experiments, 122 WT, 99 HTT_SA and 109 HTT_SD dendrites, 1171 WT, 1119 HTT_SA and 1074 HTT_SD vesicles. Significance was determined using an unpaired t-test; *p<0.05; ns = not significant. Scale bar = 20 µm. (see also Video 3).

Figure 3—figure supplement 1. Cellular distribution of kinesin and dynactin in WT and HTT_SA mouse brains.

Total, vesicular and cytosolic fractionations were analyzed by western blot using KHC, p150 (fractionation control) and tubulin (loading control) antibodies. (A) KHC signal was quantified in total fraction as the ratio of KHC signal on tubulin signal. (B) Vesicular KHC signal was normalized on cytosolic signal. Graphs represent three brains per genotype analyzed with two independent experiments. Significance was determined using Mann-Whitney test. p=0,09.