Fig. 1

Microglia depletion and repopulation prevents long-term radiation-induced memory deficits and loss of hippocampal PSD95. a Experimental design and Novel Object Recognition (NOR) test result. CSF-1R inhibitor was used to deplete microglia during 3 doses of 3.3 Gy of whole-brain radiotherapy (WBRT). A 4-day NOR protocol was used to measure recognition memory, which ended on day 32 post WBRT. Microglia were isolated using fluorescent activated cell sorting (FACS) on day 33 and dot plots showing NOR results. Statistical analysis was performed using two-way ANOVA with Dunnett’s multiple comparisons test. There is no CSF-1Ri treatment effect (F (1, 38) = 1.787, p = 0.1893), but significant WBRT effect (F (1, 38) = 13.23, p = 0.0008) and interaction between CSF-1Ri treatment and WBRT (F (1,38) = 6.07, p = 0.0184), N = 9–12, animals with insufficient exploration time on NOR test day were excluded. b Hierarchically clustered heatmap showing significantly altered microglial genes by WBRT, but not changed with CSF-1Ri treatment. c Bar graphs summarizing fold enrichment and p values of the top 20 enriched Biological Processes by Gene Ontology analysis from up-regulated microglial genes after WBRT (full list in Additional file 2: Table S1). No significantly enriched terms were identified by GO analysis from down-regulated genes by WBRT. d A pie chart summarizing all enriched GOBP terms. ns = not significant, ***p < 0.0001. e Scatter plots showing gating strategy in flow synaptometry analyses. Fluorescent beads at various sizes were used as standard to gate isolated hippocampal cell membrane fractions. Particles between 1 µm and 3 µm were considered synaptosomes and used to determine Synapsin 1 and PSD95 protein levels by mean fluorescent intensities (MFIs). f Dot plots to compare Synapsin 1 and PSD95 MFI levels in hippocampal cell fractions. Statistical analyses were performed using two-way ANOVA with Tukey’s multiple comparisons test. ns = not significant, *p < 0.05, ***p < 0.001. N = 6