Mutation: In order to mimic human Apo E4 isoform, site-directed mutagenesis by PCR
was used to exhange a G for a C at last nucleotide position of exon 3 of mouse APOE
gene (thereby changing the threonine-61 to arginine)
Vector: Targeting vector included a floxed neomycin (neo) cassette that could later
be removed by crossbreeding with the Cre-deleter mouse (Meyers, 1998)
Mouse Strain: C57BL/6
In heterozygous mice with neo casette excised (Arg-61 mice), apoE plasma levels
were only 60-70 percent those of wild-type apoE, indicating that the humanized apoE
is catabolized more rapidly.
Relative to wt apoE, Arg-61 apoE bound prerentially to lower density lipoproteins,
and little or no Arg-61 apoE was found to bind to high density lipoproteins.
When neo cassette was left in, mice with Arg-61 were hypomorphic for apoE, expressing
only about 5 percent of normal apoE mRNA and 2 - 5 percent of normal apoE plasma
In study by Raffai and Weisgraber (2002), the lipoprotein profile of the hypomorphic
Arg-61 apoE (hypoE) mice was near normal on a chow diet. However, unlike wt apoE
mice, the hypoE mice were susceptible to diet-induced hypercholesterolemia. This
condition was completely reversible within 3 weeks of return to chow diet.
The hypercholesterolemia can also be reversed by conditional gene repair in a cross
between hypoE mice and an inducible Mx1-Cre mouse. A single intraperitoneal injection
of 250 mg of pIpC in these mice restored plasma apoE levels in 10 days, completely
reversing the diet-induced hypercholesterolemia. (Raffai, 2002)
Raffai RL, Dong LM, Farese RV Jr, Weisgraber KH. Introduction of human apolipoprotein
E4 "domain interaction" into mouse apolipoprotein E. Proc Natl Acad Sci U S A. 2001
Raffai RL, Weisgrager KH. Hypomorphic apolipoprotein E mice: A new model of conditional
gene repair to examine apolipoprotein E-mediated metabolism. J Biol Chem. 2002 Mar
Meyers EN, Lewandoski M, Martin GR. An Fgf8 mutant allelic series generated by Cre-
and Flp-mediated recombination. Nat Genet. 1998 Feb;18(2):136-41.