Biologists have understood the broad contours of the rules of inheritance for more than a century: that genes are passed down from parent to child within species. But in more recent years, they have also become aware of genes that go rogue and hop laterally between species — be they frog genes in Madagascar that originally came from snakes, or antifreeze genes found in cold-water fish like herring that transferred to smelts. The mechanism facilitating this gene transfer has been unclear, though viruses were suspected to play a role.
In new research published in Science, researchers have identified a unique class of genetic elements as the agents responsible for shuttling certain genes between multiple species of simple invertebrates called roundworms. A jump from one worm to another may not sound like much, but the worms in question diverged many millions of years ago, making them as different at the molecular level as fish and humans. The genetic elements, called Mavericks, have been detected in a wide range of animals, both invertebrates and vertebrates, and they display many features found in the genomes of viruses. Given those properties, researchers suspect that Mavericks — and similar elements, including some not yet discovered — may have mediated horizontal gene transfers throughout the history of life.
While bacteria, viruses and many protists frequently exchange DNA, multicellular animals have protective barriers around their reproductive cells that generally prevent the uptake of foreign DNA. Irina Arkhipova, a molecular geneticist at the Marine Biological Laboratory in Woods Hole, Massachusetts, who was not involved in the research, said that it reveals how the “barriers can occasionally be broken” in some animal lineages to transfer genes.
For that reason, a DNA element that encodes the ability to transfer genes to the genome of a completely different species is “quite a major discovery,” said SaraH Zanders, a geneticist at the Stowers Institute for Medical Research who was also not involved in the study. [Continue reading…]