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 鈥渏umping gene鈥� 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 鈥渏unk DNA鈥�, and it is conceivable that more of these genes might become active again, says Bekpen. 鈥淒on鈥檛 count them out until they鈥檙e completely deleted,鈥� he says (PLoS Genetics, ).