Related Experiment Video
Updated: Sep 2, 2025
A Novel In Vitro Live-imaging Assay of Astrocyte-mediated Phagocytosis Using pH Indicator-conjugated Synaptosomes
Published on: February 5, 2018
Lipid accumulation induced by APOE4 impairs microglial surveillance of neuronal-network activity
Matheus B Victor1, Noelle Leary1, Xochitl Luna1
1Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
Abstract:
Apolipoprotein E4 (APOE4) is the greatest known genetic risk factor for developing sporadic Alzheimer's disease. How the interaction of APOE4 microglia with neurons differs from microglia expressing the disease-neutral APOE3 allele remains unknown. Here, we employ CRISPR-edited induced pluripotent stem cells (iPSCs) to dissect the impact of APOE4 in neuron-microglia communication. Our results reveal that APOE4 induces a lipid-accumulated state that renders microglia weakly responsive to neuronal activity. By examining the transcriptional signatures of APOE3 versus APOE4 microglia in response to neuronal conditioned media, we established that neuronal cues differentially induce a lipogenic program in APOE4 microglia that exacerbates pro-inflammatory signals. Through decreased uptake of extracellular fatty acids and lipoproteins, we identified that APOE4 microglia disrupts the coordinated activity of neuronal ensembles. These findings suggest that abnormal neuronal network-level disturbances observed in Alzheimer's disease patients harboring APOE4 may in part be triggered by impairment in lipid homeostasis in non-neuronal cells.
Insights
The APOE4 gene variant impairs microglia function in Alzheimer's disease by causing lipid accumulation, reducing neuronal responsiveness, and disrupting neural network activity. This highlights lipid homeostasis's role in APOE4-associated neurodegeneration.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- Apolipoprotein E4 (APOE4) is the primary genetic risk factor for sporadic Alzheimer's disease (AD).
- The precise mechanisms by which APOE4 influences microglia-neuron interactions in AD pathogenesis remain unclear.
Purpose of the Study:
- To investigate the functional differences between APOE4-expressing microglia and APOE3-expressing microglia in neuron-microglia communication.
- To elucidate the impact of APOE4 on microglial responses to neuronal activity and its implications for AD.
Main Methods:
- Utilized CRISPR-edited induced pluripotent stem cells (iPSCs) to model APOE3 and APOE4 expression in microglia and neurons.
- Analyzed transcriptional signatures of microglia exposed to neuronal conditioned media.
- Assessed microglial lipid accumulation and uptake of extracellular lipids.
Main Results:
- APOE4 induces a lipid-accumulated state in microglia, diminishing their responsiveness to neuronal signals.
- Neuronal cues trigger a lipogenic program in APOE4 microglia, amplifying pro-inflammatory responses.
- APOE4 microglia exhibit reduced uptake of fatty acids and lipoproteins, impairing neuronal ensemble coordination.
Conclusions:
- Impaired lipid homeostasis in APOE4 microglia contributes to disrupted neuronal network activity observed in AD.
- APOE4-driven alterations in microglial lipid metabolism represent a potential therapeutic target for Alzheimer's disease.
- This study reveals a novel mechanism linking APOE4 genotype to AD pathophysiology through microglial lipid dysregulation.
