Abstract
The rare APOE3-Christchurch (APOE3Ch) variant is linked to resistance against PSEN1 p.E280A-driven autosomal dominant Alzheimer's disease (AD). Recent studies in AD mouse models have demonstrated an effect of APOE3Ch in reducing tau pathology and tau propagation, yet its effects on amyloid pathology and related toxicity are not fully understood. While prior studies have reported reduced amyloid pathology with APOE3Ch, we extended this knowledge by investigating how astrocyte-specific expression of APOE3Ch impacts amyloid pathology and related responses in 5xFAD mice, an amyloid mouse model. Using adeno-associated virus (AAV)-mediated gene delivery, we overexpressed APOE3 or APOE3Ch in astrocytes of 5xFAD mice at the neonatal stage, then analyzed their effects during the advanced stage of amyloid pathology. Astrocytic APOE expression significantly reduced amyloid burden, neuritic dystrophy, and gliosis compared to GFP controls. Notably, astrocytic APOE3Ch expression, relative to APOE3, markedly lowered oligomeric Aβ levels and promoted the formation of more compact, fibrillar plaques, suggesting a shift toward a less toxic aggregation profile. Transcriptomic profiling of cortical tissue revealed broad downregulation of immune-related and proteostatic pathways. These findings indicate that astrocytic APOE3Ch sufficiently attenuates Aβ pathology and related toxicity, supporting its potential as a therapeutic modifier for AD.