Prior investigations have provided evidence indicating a diminished capacity for cholesterol synthesis in the brains of individuals diagnosed with AD [29], and that levels of the key proteases 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and 3beta-hydroxysterol-delta24 reductase (DHCR24), which mediate cholesterol synthesis, are reduced [30,31]. The gene discussed is DHCR24; the disease is Alzheimer disease.