Apolipoprotein E polymorphisms and female fertility in a transgenic mouse model of Alzheimer's disease.

Apolipoprotein E (APOE) is a major cholesterol carrier responsible for lipid transport and injury repair in the brain. The human APOE gene (h-APOE) has 3 naturally occurring alleles: ε3, the common allele; ε4, which increases Alzheimer's disease (AD) risk up to 15-fold; and ε2, the rare allele which protects against AD. Although APOE4 has negative effects on neurocognition in old age, its persistence in the population suggests a survival advantage. We investigated the relationship between APOE genotypes and fertility in EFAD mice, a transgenic mouse model expressing h-APOE. We show that APOE4 transgenic mice had the highest level of reproductive performance, followed by APOE3 and APOE2. Intriguingly, APOE3 pregnancies had more fetal resorptions and reduced fetal weights relative to APOE4 pregnancies. In conclusion, APOE genotypes impact fertility and pregnancy outcomes in female mice, in concordance with findings in human populations. These mouse models may help elucidate how h-APOE4 promotes reproductive fitness at the cost of AD in later life.