Biotech Company Creates ‘Woolly Mouse’ as a Step in Its Quest to Resurrect Woolly Mammoths Through Gene Editing

A company working on a controversial plan to “de-extinct” woolly mammoths and other creatures says it has successfully used gene editing techniques to create mice with long, golden coats.

Texas-based startup Colossal Biosciences announced this week that it had produced “woolly mice,” or rodents that its scientists had genetically engineered to have thick, fluffy, mammoth-like hair. In addition to a press release, the company described the research in a preprint paper on Tuesday that has not yet been peer reviewed.

The hairy mice are a “massive validating point” in the company’s quest to resurrect extinct species like the woolly mammoth, the thylacine and the dodo, says Ben Lamm, co-founder and CEO of Colossal Biosciences, to the Guardian’s Nicola Davis.

Scientists who are not involved with the company say they are impressed by the technical aspects of the research. But they argue that creating hairy mice is not the same as bringing back a mammoth or another extinct creature.

“As it is, we have some cute-looking hairy mice, with no understanding of their physiology, behavior, etc.,” says Robin Lovell-Badge, a geneticist at the Francis Crick Institute in London, to CNN’s Katie Hunt. “It doesn’t get them any closer to know if they would eventually be able to give an elephant useful mammoth-like traits, and we have learned little biology.”

“It’s just a mouse that has some special genes,” Stephan Riesenberg, a genome engineer at the Max Planck Institute for Evolutionary Anthropology who was not involved in the work, tells Nature News’ Ewen Callaway.

Colossal Biosciences plans to de-extinct mammoths by genetically modifying existing Asian elephants. The company wants to implant genetically engineered embryos into female elephants, in hopes that they will give birth to calves with woolly mammoth-like traits. Their goal is for the first calf to be born by 2028.

In their recent experiments with mice, the company’s scientists tweaked several genes believed to influence the rodents’ coats, such as the color, texture and length of their hair. They modified these genes to produce physical traits that resemble mammoths, such as a thick, shaggy, golden-colored coat. They also edited a gene found in both mice and mammoths that’s related to fat metabolism and may play a role in cold adaptation. Scientists tested various combinations of the different gene edits in the mice.

In some experiments, they genetically modified fertilized mouse eggs, per the Guardian. In others, they modified embryonic mouse stem cells, then injected those cells into mouse embryos. Then, they implanted either the genetically engineered eggs or embryos into female mice.

Some of the experiments resulted in the births of genetically modified baby mice, while other pregnancies were not successful. But the gene-edited mice that were born appear to be perfectly healthy, reports Wired’s Matt Reynolds. In addition, those young mice had long, thick, golden hair.

“I’m pretty skeptical about this, but that mouse is pretty adorable,” Vincent Lynch, a biologist at the University at Buffalo who was not involved in the project, tells NPR’s Rob Stein.

Researchers have not yet tested whether the gene edits had any effect on the woolly mice’s tolerance of cold temperatures. But all of them had a similar average body mass, whether or not scientists had tweaked the gene associated with fat metabolism and cold tolerance, per the Guardian.

Since the woolly mice are just a few months old, the company also has no data on how the genetic modifications might affect their long-term health and survival, reports Nature News.

Regardless, the company’s leaders say these experiments are a promising step toward their goal of engineering mammoth traits into Asian elephants. They also say the same gene-editing techniques might someday be used for other purposes, such as helping humans fend off diseases, per the Associated Press’ Christina Larson.

But outside scientists point out that working with Asian elephants will be much more difficult than working with mice, which are already regularly used in laboratory experiments. For one, Asian elephants are endangered. Scientists don’t know as much about their genome as a lab mouse’s, and the elephants’ pregnancies typically last 22 months, which is a long time to wait for results.

Beyond that, even if the company’s scientists manage to produce a mammoth-like Asian elephant, does that really mean they’ve resurrected an extinct species?

“You’re not actually resurrecting anything—you’re not bringing back the ancient past,” Christopher Preston, a scientist at the University of Montana who was not involved with the research, says to the Associated Press. “You might be able to alter the hair pattern of an Asian elephant or adapt it to the cold, but it’s not bringing back a woolly mammoth. It’s changing an Asian elephant.”

Many scientists remain skeptical of Colossal Biosciences’ mission more broadly and say the woolly mouse is just the company’s latest stunt. They argue the money would be better spent preserving and protecting existing species.

“It’s arrogance,” says Sue Lieberman, vice president of international policy at the Wildlife Conservation Society, to Scientific American’s Adam Popescu. “I’m not against technology. I’m not saying nature’s perfect. But this is such a waste of money when conservation is dying for lack of funds. To make some strange animal we can gawk at—we should be past that.”

Others have raised ethical concerns about the company’s goals and asked practical questions, such as what effect mammoth-like elephants would have on the environment.

“They sort of want to mess around on a pretty large scale,” says Karl Flessa, a geoscientist at the University of Arizona who was not involved with the research, to NPR. “I don’t know what the downside of having a bunch of hairy Asian elephants stomping around in the tundra might be. I don’t know what would happen. They don’t know what would happen. They can’t really assure me that, ‘Oh, everything will be just fine. Everything will be just like it was back in the Pleistocene.’ I’m not ready to play God like that.”