Fig. 5
Pathologic tau is secreted through microglia-derived EVs. a: The timeline of injection of mE-CD9 lentivirus and AAV-P301L-tau. b: Representative low-magnification images of the injection site in the MEC showing FSB (blue: amyloid plaque), mE-CD9 (green), Mac2 (red), and AT8 (magenta). c: Left: Representative images of homeostatic microglia (Mac2−) and MGnD (Mac2+) with phagocytosed AT8+ p-tau and secreted mE-CD9+ EVs (white) surrounding microglia. Right: Surface rendering images by IMARIS software showing internalized p-tau within microglia or EVs. d: Representative images of microglia-derived mE-CD9+ EVs (white) containing p-tau (magenta). See also Supplementary Video S3. e: Immuno-gold electron microscopy images of microglia-derived EV containing mE-CD9 fusion protein (GFP+ 10 nm immuno-gold dots) and p-tau (AT8+ 5 nm immuno-gold dots). f: Quantification of mE-CD9+ EVs released from homeostatic microglia (Mac2−) and MGnD (Mac2+) in the injected region. g: Volume of phagocytosed p-tau per microglia h: Quantification of total p-tau released through mE-CD9+ EVs per microglia. Representative images displayed in a-h are a mix of male and female mice. f-h: n = 8 microglia per group from 5 WT and 5 AppNL-G-F animals. Graphs comparing values across all 4 groups were analyzed via 2-way analysis of variance (ANOVA) with Tukey post-hoc analysis for individual comparisons. * p < 0.05 between indicated groups, # p < 0.05, ## p < 0.01 for the Mac2 factor