<Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> </Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> <P> Apolipoprotein E (ApoE) is a class of apolipoprotein found in the chylomicron and Intermediate - density lipoprotein (IDLs) that is essential for the normal catabolism of triglyceride - rich lipoprotein constituents . In peripheral tissues, ApoE is primarily produced by the liver and macrophages, and mediates cholesterol metabolism in an isoform - dependent manner . In the central nervous system, ApoE is mainly produced by astrocytes, and transports cholesterol to neurons via ApoE receptors, which are members of the low density lipoprotein receptor gene family . ApoE is the principal cholesterol carrier in the brain . This protein is involved in Alzheimer's disease and cardiovascular disease . </P> <P> The gene, APOE, is mapped to chromosome 19 in a cluster with apolipoprotein C1 and the apolipoprotein C2 . The APOE gene consists of four exons and three introns, totaling 3597 base pairs . APOE is transcriptionally activated by the liver X receptor (an important regulator of cholesterol, fatty acid, and glucose homeostasis) and peroxisome proliferator - activated receptor γ, nuclear receptors that form heterodimers with retinoid X receptors . In melanocytic cells APOE gene expression may be regulated by MITF . </P>

Apolipoprotein e4 appears to play a role in