Previous studies found that there is a significant reduction in the expression of new gene in specific vulnerable brain regions in Alzheimer's disease (AD) patients, which was named selective AD indicator 1 (Seladin-1), or 3β-hydroxysterol-Δ24 reductase (DHCR24) (Greeve et al., 2000; Waterham et al., 2001). The gene discussed is DHCR24; the disease is Alzheimer disease.