R01AG082362

Elucidating endolysosomal trafficking dysregulation induced by APOE4 in human astrocytes - 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 APOE4 (APOE4/4) 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 APOE4/4 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 APOE4/4 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 APOE4/4 astrocytes in transcriptional and functional changes. The identified phenotypes will be validated in AD post-mortem brain. In Aim 2, using CRISPRi screen on APOE4/4 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 project sets out to uncover potential therapeutic drug targets to tackle APOE4-driven endolysosomal trafficking endophenotypes found in APOE4 carrier AD patients.

Trustees Of Boston University

TO ENCOURAGE BIOMEDICAL, SOCIAL, AND BEHAVIORAL RESEARCH AND RESEARCH TRAINING DIRECTED TOWARD GREATER UNDERSTANDING OF THE AGING PROCESS AND THE DISEASES, SPECIAL PROBLEMS, AND NEEDS OF PEOPLE AS THEY AGE. THE NATIONAL INSTITUTE ON AGING HAS ESTABLISHED PROGRAMS TO PURSUE THESE GOALS. THE DIVISION OF AGING BIOLOGY EMPHASIZES UNDERSTANDING THE BASIC BIOLOGICAL PROCESSES OF AGING. THE DIVISION OF GERIATRICS AND CLINICAL GERONTOLOGY SUPPORTS RESEARCH TO IMPROVE THE ABILITIES OF HEALTH CARE PRACTITIONERS TO RESPOND TO THE DISEASES AND OTHER CLINICAL PROBLEMS OF OLDER PEOPLE. THE DIVISION OF BEHAVIORAL AND SOCIAL RESEARCH SUPPORTS RESEARCH THAT WILL LEAD TO GREATER UNDERSTANDING OF THE SOCIAL, CULTURAL, ECONOMIC AND PSYCHOLOGICAL FACTORS THAT AFFECT BOTH THE PROCESS OF GROWING OLD AND THE PLACE OF OLDER PEOPLE IN SOCIETY. THE DIVISION OF NEUROSCIENCE FOSTERS RESEARCH CONCERNED WITH THE AGE-RELATED CHANGES IN THE NERVOUS SYSTEM AS WELL AS THE RELATED SENSORY, PERCEPTUAL, AND COGNITIVE PROCESSES ASSOCIATED WITH AGING AND HAS A SPECIAL EMPHASIS ON ALZHEIMER'S DISEASE. SMALL BUSINESS INNOVATION RESEARCH (SBIR) PROGRAM: TO EXPAND AND IMPROVE THE SBIR PROGRAM; TO INCREASE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT; TO INCREASE SMALL BUSINESS PARTICIPATION IN FEDERAL RESEARCH AND DEVELOPMENT; AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION. SMALL BUSINESS TECHNOLOGY TRANSFER (STTR) PROGRAM: TO STIMULATE AND FOSTER SCIENTIFIC AND TECHNOLOGICAL INNOVATION THROUGH COOPERATIVE RESEARCH DEVELOPMENT CARRIED OUT BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS; TO FOSTER TECHNOLOGY TRANSFER BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS; TO INCREASE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT; AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION.

93.866 - Aging Research

National Institute on Aging (NIA) [HHS - NIH]

Boston, Massachusetts 021182518 United States

Single Zip Code

Research on Current Topics in Alzheimer's Disease and Its Related Dementias (R01 Clinical Trial Optional) (PAR-22-093)

Amendment Since initial award the total obligations have increased 109% from $1,585,868 to $3,312,642.