A GENE active in humans today died out during our primate evolution and then came back to life again. This is first time such a resurrected gene has been seen.
The IRGM gene protects us from several diseases, including TB. When , at the University of Washington in Seattle, traced the gene back through our primate ancestry, he got a surprise. While mouse lemurs (pictured) have a functional copy of IRGM, Bekpen found that the macaque version is useless. But chimps and gorillas, like us, have a functional gene.
So the gene must have been extinguished after apes and monkeys separated from the other primates. Bekpen found that a “jumping gene” called Alu disrupted the sequence of IRGM and essentially killed it off.
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Then another genetic marauder moved in after macaques branched off. ERV9 is an endogenous retrovirus, a long-term resident of the human genome. It revitalised IRGM by acting as a signpost to enzymes that read our DNA.
Humans have a lot of inactive genes, often called “junk DNA”, and it is conceivable that more of these genes might become active again, says Bekpen. “Don’t count them out until they’re completely deleted,” he says (PLoS Genetics, ).
