APOE

What is APOE?

APOE, formally known as apolipoprotein E (APO E), is a gene present in chromosome 23 of all humans, currently used as a marker to determine the potential predisposition to develop Alzheimer’s disease. There are three manifestations of the gene and a particular expression of it has been linked to a higher risk to develop the disease, although Alzheimer’s may occur in the presence of any of them. The 3 gene manifestations associated with different levels of risk to develop Alzheimer’s disease are:

• APOE e2 – This is the least commonly found gene and has actually been found to have a reduced risk of the onset of Alzheimer’s disease.
• APOE e3 – This is the most commonly found gene but it has NOT been associated with any change in risk of the development of Alzheimer’s disease.
• APOE e4 – This gene has been found to be linked to the increased occurrence of Alzheimer’s disease in individuals who carry this gene. 

Understanding the expression of the APOE gene:

• Each person inherits one APOE gene (allele), from their mother and one from their father.
• There are 6 possible APOE gene combinations: e2-e2, e2-e3, e2-e4, e3-e3, e3-e4, e4-e4
• The e4 subtype increases the chances of getting Alzheimer’s disease.
• If both genes are positive for the e4 subtype the chances of developing Alzheimer’s increases even more. 
• APOE is not the only gene risk factor. Researchers are studying other potential genes affecting the illness risk as well.
• Just because an individual has one or both APOE e4 positive alleles, does not mean that they will develop Alzheimer’s, nor are APOE e4 negative individuals exempt from developing the disease.
• The APOE e4 gene is a marker among others associated with risk to develop the disease; but not the direct cause. Its presence does not imply that those who have it will develop the disease.