“It is arguably the genetic technology with more social, ethical and policy implications than any other to emerge in the last decade,” Sally Otto, a University of British Columbia zoologist, wrote on the Royal Society of Canada website.
“Gene drive could be used to spread genes that reduce the ability of mosquitoes to transmit … diseases, including malaria, zika and dengue, that kill half a million people (annually) worldwide…. Gene drive could also be used to reduce the spread of invasive species, either sterilizing them or skewing their sex ratios towards males.”
Gene drive, in basic terms, is a tool to spread a genetic alteration into a wild population of a certain species.
In nature there is on average a 50 percent chance of a parent passing a particular trait to an offspring.
However, with a gene drive a specified gene is inherited by all offspring, even if it is present in only one parent.
A U.S. National Academy of Sciences report said that in 2015 researchers used a gene-editing technique called CRISPR/Cas 9 to drive a targeted gene through about 99 percent of a population of fruit flies and mosquitoes.
The research was done in a lab rather than in the field.
The groundbreaking science switched on a light bulb for biologists around the globe. Many scientists are now exploring possible uses for gene drive, including:
- altering the genetics of mosquito populations so they can’t transmit diseases
- reducing the population of mosquitoes by making females sterile
- altering the genetics of insect pests so they can’t transmit diseases to crops
Entomologists are particularly interested in the potential of the technology because insects reproduce frequently, making it possible to drive a desired genetic trait through a large population of insects in a short period of time.
The trait could be something like sterility, which would reduce the overall population of pests.
“Researchers are pursuing applications of gene drives to control a number of economically significant agricultural pests. These include Lepidopteran insects … and spotted wing Drosophila, one of the most significant pests of small fruit and berry producers in the United States,” Zachary Brown, an economist at North Carolina State, wrote in Choices, a magazine of the U.S. Agricultural Economics Association.
The opportunity to control agricultural pests could be limitless, but many scientists are worried about the possibilities made famous by former U.S. Defense Secretary Donald Rumsfeld: the known unknowns and unknown unknowns of gene drive.
One of the major concerns is that it’s more powerful than established biotechnology.
“It has great potential, which is why people are quite interested in it,” Otto said.
“What’s different about this technology is it’s not just capable of modifying a single organism, but spreading throughout a species…. (It’s) a much broader implication than genetic engineering of a single individual.”
Johanna Elsensohn, a graduate student in entomology at North Carolina State University, said a gene drive to control mosquitoes in South America could potentially alter the mosquito population in North America.
“Potentially, over time, over many, many generations, if you released it in Brazil it could make it to the U.S,” said Elsensohn, co-author of a scientific paper looking at the obstacles and challenges of using gene drive in agriculture.
Controlling the geographic spread of the gene is worrisome, as is the remote possibility of the gene spreading to other species.
For Patrick Tranel, a weed scientist at the University of Illinois, the technical reality of gene drive is forcing policy makers to answer a profound question: is it ethical to extinguish a species, even a pest that spreads disease?
“There are very few organisms in the world that we have enough understanding that we would want to (drive it) to extinction,” he said.
“I don’t want to play God, at that level, to decide that this species has absolutely no value to Earth.”
There’s also the secondary impact of that extinction. What would the loss of an insect species mean to bats and birds that feed on that insect?
How does the loss of that insect, or a reduced population, affect the entire ecosystem?
Most of the funding and the majority of scientific activity is being dedicated to gene drive and insect pests, but some researchers are looking into gene drive and weeds.
Despite his reservations, Tranel believes gene drive could be used to control troublesome weeds that are resistant to multiple herbicides.
He is studying the dioecious nature of certain weeds, in which there are male flowers and female flowers on separate plants. If weed scientists can understand how that works genetically, it could lead to a gene drive.
“We could (hypothetically) control maleness and make males the dominant trait in these weeds. We could release some males that are modified so that all of their progeny would be males,” he said.
“And after a few generations you would eliminate female (weeds) from the population. Locally you could drive the population to extinction.”
Such a concept is just a concept because scientists don’t know what gene, or likely genes, determines if a weed becomes a male or female.
“In order to do a gene drive, you have to have a gene. You need a target.”
Developing a gene drive to control a weed population might be technically possible, but regulations could thwart the technology before it reached the market.
Government agencies may not accept the idea of using a gene drive to eradicate a weed or an insect that transmits disease to crops.
“Maybe an argument could be made to (make) a mosquito extinct, but I’m not sure we could make an argument saying we want a (certain) weed species extinct,” Tranel said, adding that birds eat weed seeds and that weeds are part of the ecosystem.
Another challenge, especially with a gene drive for a crop pest, is the return on investment.
What farmer is going to pay to release a gene drive moth on his cropland if the benefits go to all the growers in the region?
“Insects can go anywhere. They can fly off your farm as soon as you release them,” Elsensohn said.
“An individual has no incentive to deploy this by themselves…. This is something that would have to be adopted and released on an area-wide basis, but (ag companies) make the most of their money on individual farmer adoption.”
This sort of challenge remains a ways off because most gene drive research for agriculture is at the laboratory stage, Elsensohn said.
Otto said she’s not aware of any researchers in Canada who are using CRISPR to develop a gene drive application.
Using CRISPR gene editing to construct a gene drive has been around only since 2015, but the scientific and ethical debate over the technology is becoming louder.
A number of biologists say the only option is a complete ban of gene drive because there are too many unknowns.
Others say the technology should be considered because hundreds of thousands of people die every year from malaria and other mosquito-transmitted diseases.
Gene drive could also be used to control invasive species that cause environmental destruction.
Elsensohn thinks gene drive will first be employed to prevent the spread of disease. Adopting it for agriculture could prove difficult.
“For public health there seems to be an upswell of support. I don’t think the same can be said when you’re using that same technology for agriculture.”
That’s partly because many people remain concerned about genetically modified crops, which have been around for more than 20 years.
Polling in 2016 and 2017 shows that 40 to 50 percent of North Americans think GM food is bad for their health.
With that level of public distrust, developers of gene drive technology for agriculture could face massive public opposition and severe regulatory hurdles.
Tranel said it might take a crisis to get the public on board, something like herbicide resistant weeds destroying millions of acres of cropland in the U.S. Midwest.
“We’re not there yet … but we are in the process of running out of options (to kill weeds),” he said.
“Maybe in five to 10 years from now we’re going to need a brand new technology like a gene drive.”
- It’s a technology with incredible potential.
- It’s a technology with tremendous risks.
- It might put an end to malaria.
- It might eliminate the need for insecticides and possibly herbicides.
- It could also have tragic consequences for bats and birds.
- It could have unpredictable impacts on entire ecosystems.
The technology is called gene drive.
- In the fall of 2016 an Indian charitable foundation donated $70 million to the University of California San Diego for gene drive research. Two scientists at UC San Diego were one of the first teams to use CRISPR to construct a gene drive.
- In July of 2017, the U.S. Department of Defense’s Advanced Research Projects Agency provided $65 million in funding to seven teams of scientists to study gene drive.