School of Science Division of Life Science 15 Division of Life Science APOE Genotype-Specific Effects of Young Plasma on Cerebrovasculature and AD Pathology Supervisor: BU Guojun / LIFS Student: LOH Leyuan / BCB Course: UROP 1100, Summer Emerging evidence shows lipid droplet (LD) accumulation in hippocampal microglia of aged mice, resembling that in Alzheimer’s disease (AD) patients. iPSC-derived astrocyte and microglia studies suggest this process is mediated by apolipoprotein E (apoE) binding to LD surfaces. Given that APOE4 is the strongest genetic risk factor for AD, this study examines whether similar effects occur in brain endothelial cells (BECs) and whether LD abundance and size in BECs vary by APOE genotype. iPSCs were differentiated into BECs and analysed by immunofluorescence for LD characteristics, their colocalisation with early endosomes, perilipin-2 (PLIN2), as well as potential genotype-dependent differences in other subcellular organelles. Preliminary findings indicate more apoE and PLIN2 colocalisation with LDs in APOE2/2 BECs, whereas APOE4/4 BECs exhibit larger LDs. These observations highlight potential APOE genotype-specific effects in endothelial lipid metabolism that may influence cerebrovascular integrity and function. APOE Genotype-Specific Effects of Young Plasma on Cerebrovasculature and AD Pathology Supervisor: BU Guojun / LIFS Student: WONG Tin Lun / BCB Course: UROP 1100, Spring Apolipoprotein E (APOE) is the strongest genetic factor to Alzheimer’s disease (AD). Among the three genotypes, APOE4 is the strongest genetic risk factor while APOE2 confers protective effects compared to the most common APOE3. Recent genetic studies have also identified rare variants such as R136S (APOE3Ch) and V236E (APOE3-Jac) confers protection. This project characterized biophysical properties of this naturally occurring protective apoE (apoE3-Jac, apoE3-Ch) and apoE isoforms (apoE2/3/4) using in vitro assays. Guided by the apoE-cascade hypothesis, we evaluated the extent of oligomerization, lipidation, and heparin-binding affinity of these apoE isoforms and variants. Preliminary findings indicate that apoE3-Jac reduced oligomerization, while apoE3-Ch displays reduced heparin binding. Furthermore, biochemical assays reveal that the protective apoE2 isoform possesses a binding preference for ceramide-1-phosphate. These suggest potential mechanisms of APOE genotype-specific effects in AD pathology.
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