APOE

Apolipoprotein E is a lipoprotein, or a protein connected to a fat. Lipoproteins are responsible for carrying cholesterol and other fats through the bloodstream as little packages and are essential for the normal breakdown of these molecules. In particular, apolipoprotein E is a major component of specific lipoproteins called very low-density lipoproteins (VLDL). A major function of VLDLs is to remove excess cholesterol from the blood and carry it to the liver for processing. Maintaining normal levels of cholesterol is essential for the prevention of cardiovascular diseases, including heart attacks and strokes.

There are at least three slightly different versions of the APOE gene. The major versions, or alleles, are called e2, e3, and e4. The most common allele is e3, which is found in more than half of the population.

Alzheimer disease, type 2 - increased risk from variations of the APOE gene

People who inherit at least one copy of the APOE e4 allele have an increased risk of developing type 2 Alzheimer disease, which first appears later in life. Research has shown that people who inherit two copies of APOE e4 have the highest chance of developing the disease. It is not yet known how this allele affects a person's risk of Alzheimer disease; however, researchers have found that it increases the number of amyloid plaques, which are characteristic of the disease.

other disorders - associated with the APOE gene

Apolipoprotein E is also associated with several cardiovascular disorders. Researchers have found that most people with familial hypercholesterolemia, a condition that causes very high levels of cholesterol and an increased risk of heart attacks and strokes, have two copies of the e2 allele. This allele seems to be one of several genetic factors that play a part in this disorder. Another version of apolipoprotein E, the e4 allele, is a risk factor for coronary artery disease.

19q13.2

The APOE gene is located on the long (q) arm of chromosome 19 at position 13.2.

See How do geneticists indicate the location of a gene? in the Handbook.

You and your healthcare professional may find the following resources about APOE helpful.

• ClinicalTrials.gov - Linking patients to medical research
• Gene Reviews - Clinical summary

You may also be interested in these resources, which are designed for genetics professionals and researchers.

• PubMed - Recent literature
• OMIM - Genetic disorder catalog
• Research Resources - Tools for researchers (3 links)

See How are genetic conditions and genes named? in the Handbook.

The Handbook provides basic information about genetics in clear language.

• What is DNA?
• What is a gene?
• How does a gene make a protein?
• How can gene mutations cause disorders?

These links provide additional genetics resources that may be useful.

• Genetics education
• Human Genome Project
• Resources for Genetic Researchers

allele ; amyloid ; amyloid plaque ; cholesterol ; coronary ; familial ; gene ; heart attack ; lipoprotein ; molecule ; protein

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.