Apolipoprotein E (APOE) in the central nervous system (CNS) has been the focus of study for two reasons: it is the most abundantly expressed apolipoprotein in the CNS (Bjorkhem & Meaney, 2004; Huang & Mahley, 2014), and inheritance of the E4 allele of the APOE gene profoundly impacts the risk for Alzheimer’s disease (AD), exacerbating amyloid deposition and worsening cognition and synapse loss. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.