APOE2 attenuates APOE4-associated amyloid pathology and related toxicity in a mouse model of Alzheimer’s disease

Abstract

The apolipoprotein E (APOE) gene is the strongest genetic risk factor for Alzheimer’s disease (AD), influencing amyloid-β (Aβ) aggregation, clearance, and glial function. While APOE4 promotes Aβ pathology and APOE2 is protective, how these opposing alleles interact in the heterozygous APOE2/4 state remains unknown. Here, using littermate-controlled heterozygous APOE mice (APOE2/3, APOE3/4, and APOE2/4) alongside APOE3/3 controls crossed with 5xFAD mice, we show that APOE3/4 mice exhibit increased Aβ deposition, maladaptive microglial activation, and reduced microglial interactions with plaques. These changes were attenuated in APOE2/4 mice, accompanied by a brain proteomic profile more similar to those of APOE3/3 and APOE2/3 mice. Increased myelin basic protein (MBP) abundance was observed in APOE2/3 but not APOE2/4 mice. Plasma lipidomics revealed shared alterations in APOE3/4 and APOE2/4 mice, with distinct signatures in APOE2/3 mice. These findings define allele interaction-dependent effects of APOE on brain and systemic phenotypes and provide a framework for understanding the biological consequences of the APOE2/4 genotype. Chen and colleagues use a heterozygous mouse model carrying human APOE2 and APOE4 alleles to show that APOE2 attenuates APOE4- associated effects on brain amyloid pathology and related cellular and molecular changes.