Can genetic engineering turn the tide against Minnesota’s lake invaders?

Leland Feist and Colby Johnson carefully squeezed eggs from a female fish and sperm from a male fish, then fertilized the eggs in a Petri dish inside their St. Paul lab. Within minutes, the eggs began to divide and grow.

“We just made baby carp right there,” Johnson declared.

Not just any carp, though. These could be the newest recruits in Minnesota’s long and largely losing battle against invasive species.

Using a machine with a tiny glass needle, the researchers inject the common carp embryos with engineered DNA to introduce traits the fish could pass onto their offspring. One approach they’re testing would make female carp infertile. Another is designed to prevent female embryos from developing.

The idea is to release genetically modified male carp into a lake, where they would mate with wild female carp and pass on those genes. Eventually, the population would skew toward males, causing the carp population in that lake to dwindle, Feist said.

“The ultimate goal is to be able to manipulate the population dynamics of these fish,” he said. “If we can control how they reproduce, we can eliminate a reproducing population.”

The method has still only been tested in the lab. While the science is promising, it’s a long way from being ready to be used in Minnesota’s beloved lakes. The approach is also likely to raise ethical and policy questions.

Messing with an invader’s reproduction

Genetic engineering — altering an organism’s DNA to change its traits or add new ones — is already widely used in medicine and agriculture. But using it as an environmental tool is newer, said Nick Phelps, director of the University of Minnesota’s Aquatic Invasive Species Research Center, which is developing the genetic techniques.

“It seems a little out there, but it is the reality of where the science is now,” Phelps said “We’re really sort of forging new ground.”

“We’re still not all that close to deploying it in the field,” said Michael Smanski, a U of M professor of biochemistry and biotechnology who’s leading the common carp project. “There’s going to be a lot of laboratory tests that we need to do to make sure that it works, that it's effective, that it’s safe, that we can scale it economically.”

In other parts of the globe, genetically modified mosquitos are already being released to control disease-carrying populations. Researchers are also developing genetic approaches to control invasive rodents on some islands.

The carp fight provides a good test case for Minnesota.

Common carp are native to Europe and Asia, but they’ve spread to nearly every continent. They were introduced to Minnesota lakes as a game fish in the 1880s. The destructive fish uproot vegetation, stir up sediment and release nutrients that can contribute to algae blooms.

“They turn a biodiverse ecosystem into an ecosystem that's beneficial for them,” said Feist, a doctoral student working in the U lab. “If we can collapse those populations of invasive common carp, we can help preserve our natural bodies of water for both the wildlife and for human use.”

On a recent day in the lab, the researchers created common carp embryos so they could modify their genes early in their life cycle. By controlling light and water temperature, they had tricked the fish into thinking it’s spawning season so they didn’t have to wait until spring.

The researchers’ first test of the process was to insert a fluorescent protein gene from a jellyfish into the carp. Under blue light, the fish glow green.

Creating glowing fish isn’t the goal. But the researchers do use fluorescence to track which fish have been genetically modified.

The Minnesota scientists know genetic engineering can be controversial. They say the genetic traits they’re developing are designed to be self limiting, meaning they’ll decline and eventually disappear from the population unless researchers keep releasing modified fish.

That’s different from a self-sustaining trait designed to spread through generations.

“That gives us a level of control over the technology,” Feist said. “So if we want to stop treatment, we can stop releasing these modified fish.”

Genetic biocontrols tend to raise questions about potential impacts to public health and the environment, said Greg Kaebnick, a senior research fellow at the Hastings Center for Bioethics.

But they also can offer benefits when other strategies for controlling a destructive pest, such as trapping and poisoning, have been inadequate, Kaebnick said.

“The usual strategy for getting rid of it is itself really pretty environmentally harmful,” he said. “And some of these new strategies can be targeted exactly to the species that you’re trying to get rid of.”

Still, Kaebnick said some people will find making any sort of genetic change worrisome.

“People tend to think of the genes as sort of morally special, as sort of repositories of the essence of the species,” Kaebnick said. He said they tend to think “when you make genetic changes, you’re doing something that’s intrinsically troubling.”

‘Talk about it early and often’

Researchers at the U of M hope eventually, genetic modification techniques could be adapted to control other invasive pests, including silver and bighead carp that are moving up the Mississippi River.

They’re also working on methods of knocking down the expression of key genes in invasive zebra mussels, which have infested about 5 percent of Minnesota lakes. That project is less advanced, because while it’s fairly easy to grow common carp in a lab, they say it’s proving difficult to raise zebra mussels through their full life cycle.

But the researchers say there will need to be a public discussion over the policy, regulations and ethics of genetic biocontrol technologies before they can be widely adopted as a method of managing invasive species.

Phelps, the research center’s director, said they welcome the discussion. He said the center’s approach has been “to talk about it early and often.”

The center has convened focus groups and met with state, federal and tribal officials to discuss who decides and regulates the use of such technology, Phelps said.

They’ve also conducted surveys to gauge public attitudes, Phelps said, but found many people don’t understand how genetic modification works. Still, overall, people are more inclined to support it than the use of chemicals or pathogens to control pests, he said.

Smanski said genetic engineering isn’t a silver bullet. But he said it offers promise, and could be used alongside other control methods, such as netting and removing common carp.

“We're bringing a whole new class of technologies to bear,” Smanski said. “Even if nothing has worked in the past 100 years to get rid of this invasive species, these new technologies can really move the needle, I think.”

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