Moderator of 1 Session
Presenter of 1 Presentation
APOE Ε4 DRIVEN HUMAN SPECIFIC CHOLESTEROL TRAFFICKING DYSREGULATION IN GLIA
Abstract
Aims
The association of Apolipoprotein E (APOE) ɛ4 with Alzheimer's disease risk is well-established however, the impact of APOE ɛ4 on human brain cell function remains unclear. We hypothesized that human APOE ε4/ε4 genotype contributes to disease risk through cell autonomous and non-cell autonomous mechanisms in a human specific manner.
Methods
Global transcriptomic analyses were performed on astrocytes, microglia, mixed cortical cultures (neurons and astrocytes) and brain microvascular endothelial cells derived from human induced pluripotent stem cells (iPSCs), post-mortem brains and microglia and astrocytes from APOE targeted replacement (TR) mice. Lipid pathway dysregulation identified through GSEA, WGCNA and cell type deconvolution was validated in vitro using Gas Chromatography-Mass Spectrometry (GC-MS) to measure intracellular cholesterol and filipin staining with immunocytochemistry and western blotting to determine the subcellular compartment that accumulates cholesterol in iPSC-based models, and further confirmed by immunohistochemical analysis in human APOE4 post-mortem brain.
Results
Global transcriptomic analyses reveal that APOE 44 drives lipid metabolic dysregulation in astrocytes and microglia from human iPSCs and cell type-deconvolved post-mortem AD brain but not in primary murine APOE 44 astrocytes and microglia. APOE ε4 leads to elevated de novo cholesterol synthesis despite the intracellular accumulation of free cholesterol coupled with decreased efflux due to lysosomal cholesterol sequestration in iPSC-derived astrocytes and in hippocampal astrocytes from APOE ε4 human brain.
Conclusions
Human APOE ε4 causes human glia-specific, region-specific, cell autonomous lipid dysregulation that may increase AD risk.