Uncovering cellular pathways of Alzheimer's disease resilience driven by APOE protective variants - Project Summary/Abstract Alzheimer’s disease (AD) affects over 55 million people worldwide and remains without effective disease- modifying therapies. The apolipoprotein E (APOE) gene is the strongest genetic determinant of AD risk. While the APOE4 allele increases susceptibility and accelerates disease onset, several rare APOE variants, APOE3- Christchurch (E3R136S), APOE3-Jacksonville (E3V236E), and APOE4-R251G (E4R251G), are associated with remarkable protection, even in individuals with high-risk genetic backgrounds. These naturally protective variants offer a unique window into mechanisms of resilience that may be harnessed to prevent neurodegeneration; however, the cellular pathways through which these variants confer protection remain poorly understood. Microglia, the brain’s resident immune and degradative cells, are now recognized as critical regulators of disease risk and progression. They depend on balanced lipid metabolism and lysosomal degradation to clear debris, recycle lipids, and maintain homeostasis. APOE4 disrupts these processes, leading to lipid and protein accumulation, chronic inflammation, and neuronal injury. In contrast, preliminary data show that E3R136S microglia display enhanced lysosomal activity and reduced lipid droplet burden, suggesting that protective APOE variants preserve degradative efficiency and metabolic balance. This proposal aims to define how APOE protective variants promote microglial and neuronal resilience through three integrated aims. Aim 1 will identify conserved and variant-specific transcriptional signatures of protection in human iPSC-derived microglia and leverage computational connectivity mapping to identify small molecules that mimic these states. Aim 2 will determine whether enhanced lipid handling and lysosomal function are conserved across APOE protective variants, revealing shared mechanisms of metabolic resilience. Aim 3 will assess how microglia expressing protective APOE variants influence neuronal lipid accumulation, morphology, and function, defining how microglia-neuron lipid crosstalk supports neuronal health. To execute this interdisciplinary work and prepare for an independent research career, the investigator, Amira Affaneh, will receive advanced training in bioinformatics, APOE-regulated microglial pathways, and autophagy/lipid regulation under the guidance of mentors with complementary expertise, including Drs. Celeste Karch, Carlos Cruchaga, and David Holtzman. This project will establish a framework for reprogramming microglia toward protective states and identify molecular targets for resilience-based therapeutic strategies, ultimately uncovering fundamental pathways of protection in Alzheimer’s disease.
