JIP3 haploinsufficiency exacerbates in vivo Aβ42 levels and the development of amyloid plaque pathology. (A) Lysosomes (LAMP1, green) and amyloid plaque (Aβ, red) labeling in stitched confocal images of the cerebral cortex of 5xFAD and JIP3+/−; 5xFAD littermates. Bars, 100 µm. (B) High-magnification images of Aβ deposits and their surrounding lysosome-filled dystrophic axons from 5xFAD and JIP3+/−; 5xFAD littermates. Bars, 10 µm. (C) Quantification of the plaque burden (area occupied by plaques, normalized to 5xFAD sample) in three pairs of 5xFAD controls and JIP3+/−; 5xFAD gender-matched littermates. ***, P < 0.001, unpaired t test. (D) Area of individual plaques as defined by Aβ signal in JIP3+/−; 5xFAD animals normalized to their corresponding gender-matched 5xFAD littermates (n = 5 pairs of gender-matched littermates, 45–50 plaques measured per animal per genotype; ***, P < 0.001, unpaired t test). (E) Quantification of the area of individual dystrophic axon cross sections (LAMP1 signal) in JIP3+/−; 5xFAD animals normalized to their corresponding gender-matched littermates (45–50 accumulations per genotype per animal were analyzed; **,P < 0.01, unpaired t test). (F) Cumulative frequency distribution of the number of axonal swellings per plaque in both 5xFAD and JIP3+/−; 5xFAD littermates (***, P < 0.001, Kolmogorov–Smirnov test). (G) Quantification of soluble Aβ42 (outside of plaques) levels in brain homogenates from three pairs of 5xFAD and JIP3+/−; 5xFAD gender-matched littermates (**, P < 0.01, unpaired t test). (H) Quantification of JIP3 protein levels from three pairs of 5xFAD and JIP3+/−; 5xFAD littermates (***, P < 0.001, unpaired t test). Data presented as mean ± SD in C–E, G, and H.