# Elucidating endolysosomal trafficking dysregulation induced by APOE4 in human astrocytes

> **NIH NIH R01** · BOSTON UNIVERSITY MEDICAL CAMPUS · 2024 · $78,276

## Abstract

Project Summary
Alzheimer’s disease (AD) is the most common form of dementia without effective treatments, underscoring the
need for a better understanding of AD pathogenesis. Longitudinal studies in autosomal dominant and sporadic
AD have demonstrated that pathology begins 10-20 years before clinical symptoms, but developmental effects
of AD-associated genetic variants likely provide a substrate for future neuropathological changes. Many AD
causal GWAS variants are associated with genes involved in endolysosomal pathways in glia. However, how
these causal genes are affecting cellular mechanisms has to be further investigated to tackle the disease. One
of the important questions is whether these endolysosomal pathway genes converge on ideally one clear
phenotype that can be targeted for therapeutics. Among others, Apolipoprotein E (APOE) is the most significant
risk for late-onset AD—homozygosity for the risk allele APOE ɛ4 (APOE 44) increases AD risk by more than 15-
fold. To comprehensively assess the effect of human APOE4 on human brain cell types, we characterized the
APOE4 genotype-phenotype relationship in four brain cell types: microglia, astrocytes, brain microvascular
endothelial cells and mixed cortical cultures derived from human induced pluripotent stem cells (iPSCs). Global
transcriptome analyses and in vitro mechanism study reveal that human APOE 44 astrocytes sequester
cholesterol in lysosomes, leading to upregulated cholesterol biosynthesis despite elevated intracellular
cholesterol. Our data suggests that the APOE4-mediated lipid accumulation impairs multiple intracellular
trafficking pathways that converge on the lysosome. Therefore, we hypothesize that intracellular lipid
accumulation in APOE 44 astrocytes jams trafficking to the lysosome (Aim 1), which are controlled by upstream
regulators that can be identified by CRISPRi genetic screening (Aim 2). The APOE4-led endolysosomal defects
in vitro astrocytes can be exacerbated in vivo by excessive lipid challenge induced by neurodegeneration (Aim
3). To test these hypotheses, in Aim 1, we will determine the mechanistic defects of lipid-mediated
endolysosomal trafficking in vitro human APOE 44 astrocytes in transcriptional and functional changes. The
identified phenotypes will be validated in AD post-mortem brain. In Aim 2, using CRISPRi screen on APOE 44
astrocytes, we will identify targets to reverse defected phagocytosis and intracellular lipid accumulation and
determine the mechanisms by CROP-seq. In Aim 3, we will investigate mechanistic endolysosomal defects in
vivo xenotransplanted astrocytes at baseline and during demyelination-associated lipid debris challenge and
further test if CRISPRi-targeted astrocytes exhibit rescued phenotypes in vivo. The goal of this project is to
assess the molecular mechanisms of APOE4-driven endolysosomal and autophagic defects in lipid trafficking
and identify regulatory targets that reverse the phenotype. Further, this proposed research proje...

## Key facts

- **NIH application ID:** 11075982
- **Project number:** 3R01AG082362-02S1
- **Recipient organization:** BOSTON UNIVERSITY MEDICAL CAMPUS
- **Principal Investigator:** Julia TCW
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $78,276
- **Award type:** 3
- **Project period:** 2023-04-01 → 2028-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11075982

## Citation

> US National Institutes of Health, RePORTER application 11075982, Elucidating endolysosomal trafficking dysregulation induced by APOE4 in human astrocytes (3R01AG082362-02S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/11075982. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*