US company Colossal Biosciences has announced the creation of a “woolly mouse”—a laboratory mouse with a series of genetic modifications that lead to a woolly coat. The company claims this is the first step toward “de-extincting” the woolly mammoth.
The successful genetic modification of a laboratory mouse is a testament to the progress science has made in understanding gene function, developmental biology and genome editing. But does a woolly mouse really teach us anything about the woolly mammoth?
What has been genetically modified?
Woolly mammoths were cold-adapted members of the elephant family, which disappeared from mainland Siberia at the end of the last Ice Age around 10,000 years ago. The last surviving population, on Wrangel Island in the Arctic Ocean, went extinct about 4,000 years ago.
The house mouse (Mus musculus) is a far more familiar creature, which most of us know as a kitchen pest. It is also one of the most studied organisms in biology and medical research. We know more about this laboratory mouse than perhaps any other mammal besides humans.
Colossal details its new research in a pre-print paper, which has not yet been peer-reviewed. According to the paper, the researchers disrupted the normal function of seven different genes in laboratory mice via gene editing.
Six of these genes were targeted because a large body of existing research on the mouse model had already demonstrated their roles in hair-related traits, such as coat color, texture and thickness.
The modifications in a seventh gene—FABP2—was based on evidence from the woolly mammoth genome. The gene is involved in the transport of fats in the body.
Woolly mammoths had a slightly shorter version of the gene, which the researchers believe may have contributed to its adaptation to life in cold climates. However, the “woolly mice” with the mammoth-style variant of FABP2 did not show significant differences in body mass compared to regular lab mice.
What would it mean to de-extinct a species?
This work shows the promise of targeted editing of genes of known function in mice. After further testing, this technology may have a future place in conservation efforts. But it’s a long way from holding promise for de-extinction.
Colossal Biosciences claims it is on track to produce a genetically modified “mammoth-like” elephant by 2028, but what makes a mammoth unique is more than skin-deep.
De-extinction would need to go beyond modifying an existing species to show superficial traits from an extinct relative. Many aspects of an extinct species’ biology remain unknown. A woolly coat is one thing. Recreating the entire suite of adaptations, including genetic, epigenetic and behavioral traits that allowed mammoths to thrive in ice age environments, is another.
Unlike the thylacine (or Tasmanian tiger)—another species Colossal aims to resurrect—the mammoth has a close living relative in the modern Asian elephant. The closer connections between the genomes of these two species may make mammoth de-extinction more technically feasible than that of the thylacine.
But whether or not a woolly mouse brings us any closer to that prospect, this story forces us to consider some important ethical questions. Even if we could bring back the woolly mammoth, should we? Is the motivation behind this effort conservation, or entertainment? Is it ethical to bring a species back into an environment that may no longer sustain it?