Apolipoprotein E Nomenclature

The protein, apolipoprotein E, apoE

When written in lowercase, apoE refers to a protein, apolipoprotein E

ApoE4 is the protein isoform that is encoded by an individual with an APOE ε4 allele

The gene that encodes apolipoprotein E, APOE

When capitalized and italicized, APOE is the symbol for the gene that encodes the apolipoprotein E (apoE) protein

APOE has three common forms or polymorphisms, called alleles: ε2, ε3, and ε4. Note these alleles are designated with the Greek symbol epsilon and not E.

APOE genotype typically refers to both alleles that an individual carries, e.g., ε3/ε4

APOE ε4 is the high-risk polymorphism associated with Alzheimer's disease

APOE ε4 carrier status is often used to refer to whether or not individuals carry the high risk ε4 allele