Research into a genetic engineering technology that can permanently change the traits of a population or even an entire species is progressing rapidly. The approach uses gene drives—genetic elements that pass from parents to unusually high numbers of their offspring, thereby spreading through populations rather quickly. Gene drives occur naturally but can also be engineered, and doing so could be a boon to humanity in many ways. The technology has the potential to stop insects from transmitting malaria and other terrible infections, enhance crop yields by altering pests that attack plants, render corals resistant to environmental stress, and keep invasive plants and animals from destroying ecosystems. Yet investigators are deeply aware that altering or even eliminating a species could have profound consequences. In response, they are developing rules to govern the transfer of gene drives from the laboratory into future field tests and wider use.
Investigators have been considering ways to exploit gene drive to fight diseases and other problems for decades. The effort got a boost in recent years from the introduction of CRISPR gene editing, which makes it easy to insert genetic material into specific spots on chromosomes. In 2015 several papers reported the successful spread of CRISPR-based gene drives in yeast, fruit flies and mosquitoes. One demonstration drove genes for resistance to the malaria parasite through a mosquito population, which, in theory, should limit the parasite’s transmission. Another study interfered with female fertility in a different mosquito species.
This year a CRISPR gene-drive system was tested in mice by attempting to manipulate coat color. The procedure worked only in females. Even so, the results support the possibility that the technology could help eliminate or alter invasive mice or other mammalian populations that threaten crops or wildlife or transmit disease.
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The Defense Advanced Research Projects Agency (DARPA) is among the investors who are enthusiastic about the technology. It has poured $100 million into gene-drive research aimed at fighting mosquito-borne disease and invasive rodents. The Bill & Melinda Gates Foundation has invested $75 million in a research consortium working on gene drive to combat malaria.
Despite all the promise, gene drives raise many concerns. Might they inadvertently jump to, and disrupt, other species in the wild? What are the risks of eliminating selected species from an ecosystem? Could malevolent parties use gene drives as a weapon to, say, interfere with agriculture?
In an effort to avoid such dire prospects, one team has invented a switch that must be turned on by delivery of a particular substance before the gene drive will work. In parallel, multiple groups of scientists are working on protocols to guide progression through each stage of gene-drive testing. In 2016, for instance, the U.S. National Academies of Sciences, Engineering, and Medicine reviewed the research and made recommendations for responsible practices. And in 2018 a large, international working group laid out a road map for handling research from lab studies through releases in the field. The group (some of whose meetings were attended by observers from DARPA, the Gates Foundation or other agencies) modeled its recommendations on gene drive’s use to control malaria in Africa, where, it says, the public health benefit would probably be greatest.
Beyond limiting the risks of the technology itself, many investigators also want to avoid incidents and missteps that could lead to public or policy backlash. In a 2017 essay about the potential use of gene drive for eliminating pest mammals, Kevin M. Esvelt of the Massachusetts Institute of Technology and Neil J. Gemmell of the University of Otago in New Zealand fretted that an international incident could set back research by a decade or more. “For malaria alone,” they predicted, “the cost of that delay could be measured in millions of otherwise preventable deaths.”