Zhang et al. demonstrated that Aβ-plaque-associated Olig2- and NG2-expressing OPCs, but not astrocyte, microglia, or oligodendrocytes, in the brains of AD patients and APP/PS1 mice exhibit a senescence-like phenotype, characterized by increased SA-β-gal activity and increased expression of two cell cycle repressors p16 and p21 [25]. The gene discussed is PSEN1; the disease is Alzheimer disease.