As observed in AD patients, we found that DCX+ cells were markedly reduced in the hippocampus in 6-week-old 5XFAD mice even before the initiation of amyloid plaque deposition, whereas there were no significant differences in PCNA+ and SOX2+ cells, indicating that neuronal differentiation during AHN is vulnerable to soluble Aβ beginning in the early stage of AD. The gene discussed is PCNA; the disease is Alzheimer disease.