Rapid primate mutations raise evolution questions

8 Apr 2016

A new look at genetic mutations in primates has found a novel technique that both defends against disease and speeds up the evolution of a species in the process.

By looking at the virus-fighting techniques used by primates, which involve tailored enzyme creation to fight against threats, scientists from the US and Israel have established a byproduct of speedy, synchronised mutations throughout lineages.

Traditionally, mutations in the animal kingdom were thought to be random, fortuitous events that happened over millions of years. However, the current findings undermine that thinking, potentially forcing a re-evaluation of taxonomy timelines.

Friendly fire

The basics of the paper published in Genome Research rest on the inevitable multiplication of viruses that primates have had to defend against over time.

To defend against them, the APOBEC family of virus-fighting enzymes bombard the viral genome with clusters of mutations to render them unable to continue an infection.

This is all well and good, but what if these mutation clusters catch on in the long term? This is something the researchers call “friendly fire”.

Alon Keinan from Cornell and Erez Levanon from Israel’s Bar-ilan University are the researchers behind the paper, with the latter’s insistence on investigating friendly fire’s role on mutations eventually forcing Keinan into helping him study the field.

“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,” he said.

In short, they do.

Evolution with our closest cousins

The researchers looked for the signature of past mutations in humans and chimpanzees, focusing on one of the enzymes in the APOBEC family, APOBEC3, since it has expanded into several subtypes during primate evolution, each with unique mutational signatures.

They established thousands of instances of unique mutations in primates, something not found in other animals investigated, such as mice.

“What is appealing is that it’s an accelerated evolutionary mechanism that could generate a large change in a gene in a single generation,” said Levanon.

Most friendly fire is insignificant in the long run, but some waves slip through. Of these, mega-mutations occasionally occur, but even most of these are what Keinan calls “deleterious”, vanishing over time.

“But we do see a large number that survived,” said Keinan. “Importantly, those that survived are overrepresented in functionally important parts of the genome, which suggests that some of these mutations have been maintained by natural selection because they conferred an advantage.”

Chimpanzee image via Shutterstock

Updated 12.20pm, 11 April: The headline of this article was changed for increased clarity.

Gordon Hunt was a journalist with Silicon Republic