The APOE gene provides instructions for producing a protein called apolipoprotein E, which plays a role in transporting and metabolizing fats in the body, including in the brain. The APOE gene has three common variants: APOE2, APOE3, and APOE4. APOE4 is the variant most strongly associated with an increased risk of developing Alzheimer’s disease. Inheriting one copy of APOE4 from either parent increases the risk, while inheriting two copies further elevates the risk. The exact mechanisms by which APOE4 increases Alzheimer’s risk are not fully understood, but it is thought to affect the clearance and accumulation of amyloid-beta plaques in the brain, a hallmark characteristic of Alzheimer’s. APOE4 is also believed to impact neuroinflammation, tau protein abnormalities, and synaptic function, contributing to the disease’s pathogenesis. However, it is important to note that possessing the APOE4 variant does not mean a person will definitely develop Alzheimer’s, and other factors, such as lifestyle and environmental influences, also contribute to the overall risk.