Female mosquitoes that have been altered as part of a gene drive experiment
The National Academies of Sciences, Engineering and Medicine on Wednesday endorsed research on a technology known as “gene drive,” which gives humans the power for the first time to alter or eliminate entire populations of organisms in the wild — like mosquitoes, mice or plants — through deliberate genetic manipulation.
For centuries, people have tinkered in ever more precise ways with the genetic makeup of living things already well under our control: pets, farm animals, crops and assorted species of laboratory animals. But modifying wild animals has been stymied by the inability to choreograph the mating of organisms not under our dominion.
Gene drives overcome this limitation by ensuring that the chunk of genetic code containing them is transmitted to all of an individual’s offspring, even if it reduces their fitness or causes their annihilation. By linking pieces of DNA to the gene driver with new editing tools that make them easy to insert, scientists think they can spread desired traits through an entire wild species.
But the report by an advisory panel of ethicists, biologists and others for the N.A.S., which advises the federal government, underscores that there is not enough evidence about gene drives to justify the release of an altered living thing beyond the laboratory or controlled field experiments.Scientists and environmental advocates alike noted that while the report did a good job of laying out the many questions raised by gene drives, it did not provide many answers.
Some independent scientists say the report strikes a good balance by permitting more gene drive research while limiting the use of the technology. But opponents of widespread genetic engineering argue that the panel should have demanded a halt to this type of genetic editing, which has become feasible only in the last few years with the advent of the Crispr-Cas9 tool.
Some biologists have called for using gene drive to eradicate the Aedes aegypti mosquito that transmits the Zika virus as well as other pathogens, by spreading a gene that determines whether mosquitoes become male, reducing the number of females until the species can no longer reproduce.
The Bill and Melinda Gates Foundation, which helped pay for the report, has spent some $40 million on a gene drive project aimed at eradicating the species of mosquitoes that spread malaria. In agriculture, gene drive systems could destroy or modify insect pests. Other proposals involve using gene drives to squelch populations of harmful invasive species like rodents on islands, or to combat Lyme disease.
The panel also acknowledged how daunting it may be to ethically obtain consent from people whose environments might be affected by such a release. “There are few avenues for such participation,” the report noted, “and insufficient guidance on how communities can and should take part.”
Anthony James, a mosquito researcher at the University of California, Irvine, said the academies’ report was “reasonable.”
In addition, the panel cautioned that “after release into the environment, a gene drive knows no political boundaries.”
The technology also falls through the cracks of the existing regulatory systems for genetically engineered organisms in the United States and globally, the committee noted.
And it cautioned that officials should not resort to the gene drive technique under the pressure of a public health crisis like the one posed by the emergence of the Zika virus without the “phased testing” system recommended in the report.
The committee considered six case studies, including using gene drive to control mice destroying biodiversity on islands, mosquitoes infecting native Hawaiian birds with malaria, and a weed called Palmer amaranth that has become resistant to herbicides and a scourge for some farmers.
Each case carries its own risks, including the possibility that a gene drive might jump to another species, or that the suppression of one undesirable organism will lead to the emergence of another that is even worse. The report cites the difficulty in modeling the “cascade of population dynamics and evolutionary processes that could have numerous reverberating effects.”
Still, the possible benefits of the technology, the report concludes, make it important to pursue.
“The potential to reduce human suffering and ecological damage demands scientific attention,” said Elizabeth Heitman, a medical ethicist at Vanderbilt University who helped lead the committee. “Gene drive is a fascinating area of science that has promise if we can study it appropriately.”
So far, gene drive research has focused largely on mosquitoes that transmit infectious diseases to humans.
Anthony James, a mosquito researcher at the University of California, Irvine, who published a paper last year demonstrating how a gene drive might prevent mosquitoes from transmitting malaria, called the panel’s report “reasonable.”
“The key thing is there’s no moratorium,” he said.
But Kevin Esvelt, a Massachusetts Institute of Technology evolutionary biologist who has also pioneered the technology, said the report failed to adequately flag its key risk. “They assume you can safely run a contained field trial,” he said. “But anytime you release an organism with a gene drive system into the wild you must assume there is a significant chance that it will spread — globally — and factor that in.”
And environmental watchdog groups that have traditionally opposed genetic engineering argued that, in light of the risks identified in the report, it should have recommended the research be halted. Jim Thomas, the program director of the ETC Group in Montreal, said the report gave short shrift to how to prevent commercial and military interests from misusing the technology, which he said should be placed under the control of the United Nations.
“We believe that at this point it would be prudent to halt gene drive development until such safety concerns are formally addressed and clarified,” he said.
Gene drives spread a trait through a population by ensuring that it is passed to virtually all of an individual’s offspring as it reproduces, rather than the usual half. In laboratory experiments, the desired change has appeared in 99 percent of the offspring of flies and mosquitoes.
But James Bull, a researcher at the University of Texas, Austin, recently posted a draft paper outlining another risk: that the species might evolve to undermine the spread of the gene drive, making it less effective than researchers had hoped.
“There may be multiple mechanisms by which a species responds and blocks the harmful effects of these drives,” Dr. Bull said. “It’s going to depend on a lot of details, and the only way we’re going to find out is to try it.”
No comments:
Post a Comment