First 'resurrected' gene found in humansA gene that is active in humans today died out during our primate evolution and came back to life again. This is the first time such a "resurrection" event has been identified, researchers say.
The family of genes known as IRGs are essential to mouse immunity. Without the genes, for instance, a mouse exposed to salmonella will die within a couple of days. Humans, however, only have one gene from this family, IRGM, and Cemalettin Bekpen, at the University of Washington in Seattle, wanted to know why.
To find out, he examined the genes backwards through our primate ancestry. Chimps and gorillas, he discovered, were like us: they had a single truncated but functional gene. But, to his surprise, macaques, a little further back on the tree, had mutations which made their IRGM gene totally useless.
Further trawling revealed that mouse lemurs ? small nocturnal primates ? had three gene copies from that family, one of them functional. So somewhere after mouse lemurs, the gene had been functionally extinguished, and after macaques, function had been restored.
Useful junk?
After further analysis, Bekpen discovered that after apes and monkeys went their separate ways from the other primates, only a single copy of the gene from this family remained. And that single copy was obliterated by a jumping gene called Alu, which essentially killed it off.
And it was another random event ? this time the integration into the gene of an endogenous retrovirus called ERV9 ? which revived it, he found.
Humans have many genes that are at present non-functional, often considered "junk DNA" (see our feature Recipes for life: How genes evolve). Up to 60% of the genes associated with the sense of smell lie idle in humans, for instance. It is conceivable, says Bekpen, that other currently non-functional genes stored in our genome might become active again. "Don't count them out until they're completely deleted," he says.
This is the great thing about evolution. You never know what will happen next.
Topic: First 'resurrected' gene found in humans