Figure 8. Loss of TREM2 does not prevent synapse loss and activated microglia morphology.

1. Immunohistochemical analysis of synaptophysin (SPH, pink) and VGAT (yellow) in coronal brain sections. Representative images of thalamus are shown. Scalebars = 50 μm.
2. Quantification of SPH‐positive area. Three images per mouse were taken, and means were normalized to WT samples (n = 3 per genotype, female).
3. Quantification of VGAT‐positive area. Three images per mouse were taken, and means were normalized to WT samples (n = 3 per genotype, female).
4. Western blot of SPH in RIPA lysates from 14‐month‐old female WT, Grn ^−/−, Trem2 ^−/−, and Double ^−/− mice. Actin was used as loading control.
5. Quantification of SPH protein levels in D normalized to WT (n = 3).
6. Morphological analysis of cortical microglia. Representative maximum‐intensity projections of confocal z‐stack images showing IBA1⁺ microglial cells of female WT, Grn ^−/−, Trem2 ^−/−, and Double ^−/− mice (scalebar = 50 µm). Arrows point to individual microglia, which are shown as three‐dimensional reconstruction, scalebar = 10 µm.
7. Morphological differences in cortical microglia from WT, Grn ^−/−, Trem2 ^−/−, and Double ^−/− mice shown by branch volume, sphericity score, branch length, and the number of branch nodes. Statistical analysis of group difference for the morphological scores “Branch volume” (auc = 0.72), “Sphericity score” (auc = 0.82), “Branch length” (auc = 0.69), and “Number of branch nodes” (auc = 0.80) was performed using the Wilcoxon rank‐sum test with continuity correction and Bonferroni post hoc correction for multiple testing in R (version 4.0.3). Two images per mouse (n = 3 per genotype, female) were analyzed, each data point represents one microglia cell. Median and interquartile range are displayed.

Data information: Data represent mean ± SEM. For statistical analysis in B‐C and E, one‐way ANOVA with Tukey’s post hoc test of Grn ^−/−, Trem2 ^−/−, and Double ^−/− was used. Statistical significance was set at *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001, and ns, not significant.

Source data are available online for this figure.