A protein encoded by a variant of the APOE gene that is implicated in many cases of late-onset sporadic Alzheimer disease slows clearance of amyloid-β, contributing to amyloid-β build-up in the brain (Castellano JM et al. Sci Transl Med. 2011;3:89ra57).
In cognitively normal individuals who are younger than age 70 years, those with APOE ε4 protein had significantly more amyloid-β protein in the brain than individuals with either APOE ε2 and APOE ε3, the proteins encoded by other variants of the APOE gene.
Hampton T. Amyloid and Alzheimer Disease. JAMA. 2011;306(5):480. doi:10.1001/jama.2011.1086