The apolipoprotein E (ApoE) gene makes a protein which, when combined with fat, becomes a lipoprotein.
The lipoprotein ApoE is a very low-density lipoprotein, responsible in part for removing cholesterol from the bloodstream. Variations in ApoE affect cholesterol metabolism, which in turn alter your chances of having heart disease and in particular a heart attack or a stroke. Variations in ApoE are also associated with altered odds of having Alzheimer's disease and other diseases.
There are 3 allelic variants of ApoE, as defined by two SNPs, rs429358 and rs7412 known as:
The proteins produced by these genes are called ApoE2, ApoE3, and ApoE4.
The most common variant overall is the "standard" ApoE-ε3, and therefore more people inherited one ApoE-ε3 from each parent than any other of the possible pairs of variants.
Apo-ε2/ε2 - rs429358 and rs7412 (T;T) (T;T) - has the lowest risk.
Apo-ε3/ε3 - rs429358 and rs7412 (T;T) (C;C) - is the the most common.
Apo-ε4/ε4 - rs429358 and rs7412 (C;C) (C;C) - has 11 times higher increased Alzheimer's risk.