Nonetheless, several studies, mostly using immunostaining techniques, have shown that different types of cells, including astrocytes, microglia, neurons, and endothelial cells, in the AD brain express high levels of senescence-associated proteins, including cell cycle repressors p16, p53, and p21 [18,25,38,39,41,42,46,47,48,49,50], suggesting that cellular senescence may play a role in AD pathophysiology. The gene discussed is CDKN1A; the disease is Alzheimer disease.