1Anthropology, Yale University, 2Behavioral Sciences, New Iberia Research Center
Friday All day, Plaza Level
In humans, the apolipoprotein E (APOE) gene is polymorphic, with three primary alleles that differ from each other at two key nonsynonymous sites. These alleles are functionally different in how they bind to lipoprotein particles, and this genetic variation is associated with phenotypic variation for several medical traits, including cholesterol levels, cardiovascular health, Alzheimer’s disease risk, and longevity. The relative frequencies of the three primary alleles vary globally across populations. Moreover, it has been proposed that one particular allele (E3) might be a “meat-adaptive” variant associated with increased hunting and meat eating during human evolution. Studies comparing these human APOE alleles to the chimpanzee APOE sequence found that the chimpanzee sequence is most similar to the human E4 allele, although the resulting protein might function like that of the human E3 allele. This human-chimpanzee APOE comparison has been largely based on sequence data from a single chimpanzee, but it is potentially misleading to assume that chimpanzees have a single variant. To examine this, we sequenced the APOE gene, focusing on the functionally-important exons 3 and 4, in a total of 32 chimpanzees. This sample included 20 captive individuals representing the western subspecies (P. t. verus) and 12 wild individuals representing the eastern subspecies (P. t. schweinfurthii). Variation in our resulting sequences was limited to one non-coding, intronic single nucleotide polymorphism, which varied between the two subspecies. We found no coding (exon) variation within and between chimpanzee populations, supporting the claim that the human APOE polymorphisms are recently derived and human-specific.