Fig 2: Scatter plots for qPCR analyses of IL-34, CSF-1, and CSF-1R expression levels in inferior temporal gyrus (ITG), middle temporal gyrus (MTG), and cerebellum (CBM) brain RNA samples. Results on left side of figure show relative expression of IL-34 (A), CSF-1 (D), and CSF-1R (G) in ITG RNA samples from non-demented (ND), mild cognitive impairment (MCI), and Alzheimer's disease (AD) cases. Results on figures show expression of IL-34 (B), CSF-1 (E), and CSF-1R (H) in MTG RNA samples from low plaque non-demented (LPND), high plaque non-demented (HPND), and Alzheimer's disease (AD) cases. Results on right side of figure show relative expression of IL-34 (C), CSF-1 (F), and CSF-1R (I) in cerebellum RNA samples from ND, AD, and Parkinson's disease (PD) cases. Data were analyzed by one-way ANOVA with Fisher LSD post-hoc test for between group significance. Bars on figures indicate mean ± standard error of mean (SEM) for each analyses.

Fig 3: Scatter plots showing levels of expression of transcripts (FPKM) of key markers of activation and function expressed in control, IL-34, and CSF-1-stimulated human brain microglia (n = 4) for each treatment. Results were obtained by RNA sequencing. Due to the small number of cases, there was not statistically significant difference between groups in all cases, but many of the selected genes show trends for upregulation or downregulation of expression consistent with an altered phenotype of microglia. Data were analyzed by one-way ANOVA with Fisher LSD post-hoc test for between group significance. Bars on figures indicate mean ± standard error of mean (SEM) for each analyses. Significant changes were shown for expression of HLA-DRB5, CCL2, TLR2, and TLR5.

Fig 4: Effect of IL-34 on microglial functional properties. (A) ELISA measurements of CCL-2 from control, IL-34, and CSF-1 stimulated microglia. (B,C). Effect of IL-34 on levels of Aß (42) (1 µM) in treated microglia. (B) Representative western blot showing pattern of immunoreactivity for aggregated Aß in treated microglia for 24 h. (C) Quantification of Aß present in microglia after 24 h. Lane 1. Control untreated microglia: Lane 2. IL-34-treated microglia: Lane 3. Aß (1 µM) treated microglia: lane 4 IL-34, and Aß-treated microglia. (D–F) IL-34 effective at inducing significant cell division in human postmortem microglia. (D) Microglia treated without IL-34 for 4 days (representative field). (E) Microglia treated with IL-34 (100 ng/ml) showed significant increase in numbers. (F) Effect of IL-34 on total RNA yield of microglia treated for 4 days.

Fig 5: Scatter plots showing levels of expression of transcripts (FPKM) of key markers of activation and function expressed in control, IL-34, and CSF-1-stimulated human brain microglia (n = 4) for each treatment. Results were obtained by RNA sequencing. Due to the small number of cases, there was not statistically significant difference between groups in all cases, but many of the selected genes show trends for upregulation or downregulation of expression consistent with an altered phenotype of microglia. Data were analyzed by one-way ANOVA with Fisher LSD post-hoc test for between group significance. Bars on figures indicate mean ± standard error of mean (SEM) for each analyses. Significant changes were shown for expression of SYK, LAMP-1, CD68, MME, and TGFB1.