Look before it leaps An ancient mariner might help genes jump species From New Scientist: http://www.newscientist.co.uk/news/news_224433.html

A "JUMPING GENE" being used to genetically engineer organisms has crossed the species barrier at least seven times in evolutionary history, in one instance between flies and humans, according to a study commissioned by the British government. If organisms modified using this mobile element are released, there will be a risk of genes spreading to other species, the report says. The so-called mariner element can move around in the genome of individual species thanks to the transposase enzyme it encodes, which "cuts and pastes" it from one place in a cell's DNA to another. Such jumping genes litter most creatures' genomes. Their ability to insert themselves into chromosomes makes them attractive to genetic engineers as a means of moving genes from one species into another. In a project for the Ministry of Agriculture, Fisheries and Food, Andy Brass and two colleagues at the University of Manchester compared the DNA of 80 000 different organisms, using over five million sequences. They found seven pairs of similar mariner sequences. For instance, 83 per cent of the sequence in the tsetse fly Glossina palpalis, a blood-sucker that spreads human sleeping sickness, was the same as a sequence in humans. Such a close match is "strong suggestive evidence" that mariner has moved between tsetse flies and humans, Brass says. The transfer occurred recently in evolutionary terms, he thinks, although it is not clear whether mariner jumped from the fly to humans or vice versa. The researchers also found close matches between the mariner sequences in a tsetse fly and a mosquito; a bee and a blister beetle; and a cat flea and a rusty grain beetle. This shows that, while it's very rare, mariner can jump species. So if it is used to insert genes into animals, these genes might spread into other species. "It might not be the smartest thing to use," warns Brass. Dan Hartl of Harvard University, who discovered mariner in the 1980s, agrees that caution is necessary, given that we know so little about how mariner moves around. He is worried that if, for example, it were used to insert an insecticide into a food crop, it could spread the toxin to wild flowers and poison beneficial insects such as bees. "You have to tread carefully," he says. "You can't use it to move genes by just making assumptions beforehand." While no modified organisms created using mariner have reached the market yet, several groups around the world are working with it. Genetic engineers in the US have demonstrated that mariner can transfer an eye colour gene from a fly into a mosquito, while the Roslin Institute near Edinburgh has inserted mariner into chickens, with the aim of getting them to produce pharmaceuticals in their eggs. David Finnegan at the University of Edinburgh, who works with the Roslin team, accepts that mariner might enable inserted genes to jump species, but argues that it could be designed so that its transposase only functioned for a short while. "We can engineer things so that the risk is acceptably small," he says. Rob Edwards From New Scientist magazine, 24 June 2000.