Targeted Replacement of the Mouse Apolipoprotein E Gene with the Common Human APOE3 Allele Enhances Diet-induced Hypercholesterolemia and Atherosclerosis

Abstract

Apolipoprotein (apo) E, a constituent of several lipoproteins, is a ligand for the low density lipoprotein receptor, and this interaction is important for maintaining cholesterol and triglyceride homeostasis. We have used a gene replacement strategy to generate mice that express the human apoE3 isoform in place of the mouse protein. The levels of apoE mRNA in various tissues are virtually the same in the human apoE3 homozygous (3/3) mice and their littermates having the wild type mouse allele (؉/؉). Total cholesterol and triglyceride levels in fasted plasma from the 3/3 mice were not different from those in the ؉/؉ mice, when maintained on a normal (low fat) chow diet. We found, however, notable differences in the distribution of plasma lipoproteins and apolipoprotein E between the two groups: ␤-migrating lipoproteins and plasma apoB100 levels are decreased in the 3/3 mice, and the apoE distribution is shifted from high density lipoproteins to larger lipoprotein particles. In addition, the fractional catabolic rate of exogenously administered remnant particles without apoE was 6-fold slower in the 3/3 mice compared with the ؉/؉ mice. When the 3/3 and ؉/؉ animals were fed a high fat/high cholesterol diet, the 3/3 animals responded with a dramatic increase (5-fold) in total cholesterol compared with the ؉/؉ mice (1.5-fold), and after 12 weeks on this same diet the 3/3 animals developed significantly (at least 13-fold) larger atherosclerotic plaques in the aortic sinus area than the ؉/؉ animals. Thus the structural differences between human APOE3 and mouse ApoE proteins are sufficient to cause an increased susceptibility to dietary-induced hypercholesterolemia and atherosclerosis in the 3/3 mice.

Treatment of severe hypercholesterolemia in apolipoprotein E-deficient mice by intramuscular injection of plasmid DNA

“…However, apoE secretion did not reach very high levels in the sera of the experimental animals (less than 1% of the endogenous apoE level found in normal mice). 26 One possible explanation is the rapid cycling due to the high levels of cholesterol. 10 In fact, apoE protein could be quickly associated with lipids, taken up by the cells and transported to the tissues, thus resulting in a low serum concentration in these animals.…”

Human Apolipoprotein E ε4 Expression Impairs Cerebral Vascularization and Blood—Brain Barrier Function in Mice

“…In these models, the murine APOE gene of C57BL6 mice was replaced by one of three human APOE alleles (E2, E3, or E4). 21 Animals were killed at 2, 4, or 12 months of age, or 5 months for the mice used in the human immunoglobulins (hIgG) biodistribution study. All mice had free access to standard laboratory food and water and were kept on a 12-hour light-dark cycle at 22 ± 3°C.…”

Production and characterization of astrocyte-derived human apolipoprotein E isoforms from immortalized astrocytes and their interactions with amyloid-β

“…APOE knock-in mice expressing human apoE2, apoE3, or apoE4 (homozygous) under the control of the endogenous mouse apoE promoter were generated by a gene replacement strategy (Knouff et al, 1999;Sullivan et al, 1997Sullivan et al, , 1998. These mice were used to produce immortalized astrocytes.…”