APOE and early-onset autosomal dominant Alzheimer disease: Alzheimer’s disease (AD) has been reported to compromise adult neurogenesis, with AD-associated molecular players such as presenilins, Notch 1, β-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE1), apolipoprotein E (ApoE), and amyloid precursor protein (APP) having either intrinsic, or non-cell autonomous effects, that modulate adult hippocampus neurogenesis9–17.