Fig 4. TREM2 deficiency impairs microglial phagocytosis of pathological hTDP-43 protein.

hTDP-43 or GFP-hTDP-43 was expressed in the primary motor cortex of 2-month-old mice via stereotactic intracerebral injection of AAV9.CAG.hTDP-43 or AAV9.CAG.hTDP-43.GFP (AAV9.CAG.Empty or AAV9.CAG.GFP as control). a,b, Representative images (a) and quantification (b) of CD68 expression (red) in microglia (CX3CR1-GFP, green) in the primary motor cortex of indicated groups at 14 dpi. Scale bar, 100 μm. c, Representative images of CD68 (red) and CD11c (white) expression in microglia phagocytosing GFP-hTDP-43 (green) in the primary motor cortex of WT mice at 14 dpi. Scale bar, 10 μm. d,e, Representative images (d) and quantification (e) of microglia (Iba1, red) phagocytosis of GFP-hTDP-43 (green) in the primary motor cortex of indicated groups at 28 dpi, as indicated by the arrowheads. Scale bar, 20 μm. f, Analysis of co-localization of Iba1 (red curves) and GFP-hTDP-43 (green curves). Fluorescence intensity profiles of Iba1 and GFP-hTDP-43 show the distribution of fluorescence across the white dotted arrows in d. g, Representative images of co-localization of CD11c (white) with Iba1 (red) in microglia phagocytosing GFP-hTDP-43 (green) in the primary motor cortex of WT mice at 28 dpi. Scale bar, 10 μm. h, Analysis of co-localization of Iba1 (red curves), CD11c (grey curves) and GFP-hTDP-43 (green curves). Fluorescence intensity profiles of Iba1, CD11c, and GFP-hTDP-43 show the distribution of fluorescence across the yellow dotted arrows in g. Significances were calculated using either two-way ANOVA, Tukey’s post-hoc analysis (b) or two-tailed unpaired Student’s t-test (e). Data are represented as mean ± SEM. n.s., not significant, *P < 0.05, **P < 0.01, *** P < 0.001. b, n = 5 per group, P < 0.0001, F _3,12 = 36.21; e, n = 7 per group, P < 0.0001, t = 9.227, d.f. = 12.