The microglial transcriptome of a novel murine model of Alzheimer's Disease: phagocytically active and inactive microglia from homozygous App-SAA mice and WT littermate controls.

We created a novel murine model of Alzheimer's Disease using a knock-in strategy to humanize the sequence of the murine App gene and introduced three familial AD (FAD) mutations, Swedish (Swedish (KM670/671NL), Arctic (E693G)) and Austrian (T712I). To determine whether App-SAA microglia exhibit cellular dysfunctions and whether these dysfunctions relate to fibrillar Ab internalization, mice were intraperitoneally (i.p.) injected with 10 mg/kg methoxy-X04. 24 hours after injection, mice were perfused with PBS, cortical and hippocampal tissues were dissected and processed into single-cell suspension and methoxy-X04-negative and methoxy-X04-positive microglia were isolated using FACS. Mirroring our gene expression studies, we found profound alterations of the AppSAA microglia transcriptome; these changes were exacerbated in methoxy-X04 positive compared to negative cells. This experiments examines FACS-isolated microglia from 20 mice from two backgrounds (N = 10 WT, N = 10 homozygous App-SAA animals) that weren injected with 10 mg/kg methoxy-X04. Microglia were isolated from the brain (cortex & hippocampus) of each animal using FACS. In App-SAA samples, two populations of microglia cells were distinguishabe based on their methoxy-X04 staining. These populations were collected and analyzed separately as methoxy-positive and methoxy-negative fractions. In WT cells, only methoxy-negative cells were observed and processed for analysis.