The pace of evolution is typically measured in millions of years, as random, individual mutations accumulate over generations, but researchers at Cornell and Bar-Ilan Universities have uncovered a new mechanism for mutation in primates that is rapid, coordinated, and aggressive. The discovery raises questions about the accuracy of using the more typical mutation process as an estimate to date when two species diverged, as well as the extent to which this and related enzymes played a role in primate evolution.
Alon Keinan, associate professor of Biological Statistics and Computational Biology at Cornell, and Erez Levanon, co-senior author and an associate professor with the Mina and Everard Goodman Faculty of Life Sciences at Bar-Ilan University in Israel, describe the novel, and rare, process triggered by a member of the APOBEC family of virus-fighting enzymes in the journal Genome Research. As primates evolved--including chimpanzees, Neanderthals, and modern humans--the number of types of viruses tailored for targeting primates multiplied. APOBECs in our cells mount a vigorous defense, bombarding the viral genome with clusters of mutations to render them unable to continue an infection. However, having such a mutation-based defense is risky for cells, since "friendly fire" could wreak havoc on our genome as well. Indeed, the enzymes have been shown to cause mutations in the tumor cells of breast and other cancers.
"For several years, my collaborator, Erez Levanon, has been trying to convince me that we should test whether 'friendly fire' events might be passed on to subsequent generations," said Keinan. "More recently, with the mounting evidence of their role in cancer and hints of being expressed in the cells that produce sperm and eggs, we were ready to test whether the inheritance of such events has left an evolutionary impact."