Fig. 6: Astrocytes compensate for impaired microglial phagocytosis of inhibitory synapses in Trem2-deficient TauPS2APP mice.
a, Representative images of confocal z-stack and Imaris 3D reconstructions of mouse brain sections immunostained for GFAP (blue), Iba1 (white), Lamp1 (green), Homer1 (yellow) and gephyrin (red). LAMP1+ lysosomes within GFAP+ or Iba1+ volumes were classified as astrocytic or microglial lysosomes. Plaques were identified indirectly by the presence of large clusters of Lamp1 accumulation (outside of glial cell bodies), which labels dystrophic axons. In the 3D reconstructions (right hand image of each pair), only Lamp1 structures within GFAP or Iba1 volume are rendered. Scale bars, 5 µm. b,c, Fraction of Homer1 (b) or gephyrin (c) puncta identified within microglial lysosomes. d,e, Fraction of Homer1 (d) or gephyrin (e) puncta identified within astrocytic lysosomes. f,g, Ratio of Homer1 (f) and gephyrin (g) puncta within astrocytic/microglial lysosomes. Dotted line at a ratio of 1 indicates that astrocytic and microglial lysosomes contained the same number of synaptic puncta, ratio of >1 means that more synaptic puncta were localized within astrocytic lysosomes and <1 indicates that microglial lysosomes contained more synaptic puncta. Images containing dystrophic axons (plaques), were considered as ‘near plaque’ and images without any dystrophic axons were defined as ‘away plaque’. Data were analyzed by one-way ANOVA with Dunnett’s multiple comparisons test. Each dot shows average data from one mouse; n = 10–12 mice per genotype. Note that due to increased plaque load, in some TauPS2APP;Trem2KO mice we were not able to image plaque-free areas. All data are presented as mean ± s.e.m.
