APOE and Alzheimer disease: Disruption of the murine apoE gene in AD transgenic models significantly delays the formation of the so-called “dense core” Thio-S–positive amyloid plaques (Bales et al, 1997; Irizarry, Cheung et al, 2000a), even though substantial load of diffuse amyloid and elevated concentrations of soluble Aβ peptides remain in the parenchyma (Irizarry, Rebeck et al, 2000b).