Cloning to save a polecat from extinction

The black-footed polecat has almost disappeared from the face of the Earth. Miraculously rescued thanks to the American wildlife service, this cousin of the weasel suffered from a perilous defect, because all its representatives are descended from seven polecats. The risk of congenital disease has just been avoided thanks to a cloning program, a first in the history of conservation.

Mathieu Perreault
The Press

Willa and Elizabeth Ann

A black-footed polecat named Willa, who died in 1988. And another named Elizabeth Ann, born in 2021, 33 years later. Few black-footed polecats are given names. But for Ben Novak, these two animals are very special. “Elizabeth Ann is a clone of Willa, explains the biologist from the American NGO Revive & Restore. We hope, through cloning, to increase the chances of black-footed polecats surviving in the wild. They were reintroduced after disappearing, thanks to a captive breeding program. But there are only seven individuals among their ancestors. So the risk of inbreeding is very high. Cloning Willa would increase the genetic diversity of the species. »

Elizabeth Ann was born in early 2021, but she has a problem with her uterus that prevents her from reproducing. “We are going to do a second Willa cloning campaign this year,” says Mr. Novak. If it’s possible, it’s because Willa’s cells were cryopreserved at the San Diego Zoo.

Disappearance and rebirth

The black-footed polecat (also called black-footed polecat in Canada) was considered extinct in the early 1980s, but an isolated population was discovered in 1981, in Wyoming, by the US Wildlife Service. “They captured the last 24 individuals from this population in 1987, but 6 of them died soon after from a virus,” says Novak. Wildlife biologists managed to breed 14 of the 18 survivors in captivity. But because of inbreeding, there were actually only seven distinct individuals with the original lineage in captivity. »

“In the early 1990s, we began to reintroduce black-footed polecats in the states from which they had disappeared,” continues the biologist. We still maintain the breeding program in captivity, because most populations are not able to maintain themselves. So we add animals born in captivity to the populations that need them. Willa is one of six black-footed polecats captured in 1987 who died of a virus before they could breed in captivity.

There are no black-footed polecats in countries other than Canada and the United States. The black-footed polecat has disappeared due to urbanization, which has also affected its main prey, the prairie dog. In Canada, the Toronto Zoo participates in the US captive breeding program for the black-footed ferret.

The a b c of cloning

Revive & Restore takes a pet ferret egg and removes all reproductive genetic material. A few Willa cells are inserted into the pet ferret egg. The clone is then on its way. In the first round of cloning, five clones were successfully implanted into female domestic ferrets, but only Elizabeth Ann was born.

Why not use a black-footed polecat from the captive breeding program as a surrogate mother? “Because there are only 150 individuals in the program and we still need them to revive wild populations,” says Novak. The enucleated domestic ferret egg contains some genetic material, the “mitochondrial” DNA. But the amount of DNA in the mitochondria of the egg cell is 100,000 times less than the total DNA of a cell. So it doesn’t contaminate the black-footed polecat’s genome, says Novak.

The passenger pie

The other project on which Revive & Restore puts a lot of energy is the “de-extinction” by cloning of the passenger pigeon, which gave its name to the tourtière (and disappeared more than a century ago). “We would start with the eggs of a common pigeon, from which we would remove the genetic material and replace it with the genes of biological samples of passenger pigeons which have been well preserved,” says Novak. But there are still a few steps in the ethical approval of the project. »

The passenger pigeon was considered the most abundant species of bird in the world when America was discovered. The last specimen, Martha, died out at the Cincinnati Zoo in 1914. Jacques Cartier mentioned the abundance of the passenger pigeon as early as 1534 when he stopped at Île Saint-Jean, now Île -of Prince Edward Island. Hunting sounded the death knell for the passenger pigeon in the 19th century.^e century.

The ibex and the mammoth

Cloning is the dream of specialists in extinct species. In 2003, an American gene therapy company, Advanced Cell Technologies, tried unsuccessfully to clone Celia, the last ibex of the Pyrenees, captured in 1999 and died in captivity. Celia’s clone, made from a cell of her cryopreserved skin, died a few minutes after her birth due to a malformation in her lungs.

“The project that captures the public’s imagination the most is the ‘de-extinction’ of the mammoth,” says Novak. In this case, we would start from elephant eggs. The Californian biologist published in 2018 a list of a dozen animals that could be the subject of “de-extinctions”, in the journal Genoa.

Texas Cougar and Florida Panther

At least one other species has been saved from inbreeding. This is the Florida panther, saved from congenital diseases by the arrival of eight female Texas cougars in 1995. “There were only about 30 Florida cougars left,” says Mr. Novak. Many suffered from undescended testicles. But obviously, at the time, we weren’t talking about cloning. The Texas cougar is a close cousin of the Florida panther, but it is a different species. With our approach, we will preserve the genetic composition of the black-footed polecat. »

Florida vaquita

Inbreeding is not a disaster for all species. In June, biologists observed that the rarest cetacean in the world, a porpoise called a vaquita, has probably had the same number of individuals for several decades. “There are only about 10 vaquitas, a species that has been stuck for tens or hundreds of generations in the northern Gulf of California,” says Jacqueline Robinson of the University of California, San Francisco, who is the lead author. of the study published in Science.

“We have never reported vaquitas anywhere else on the planet. They get caught in the nets of fishermen and their population has declined throughout the twentieth^e century. Their secret is an innate ability to suppress dangerous genetic mutations. Other species that have survived a very small number of individuals may have the same capacity for genetic suppression, suggests the Californian biologist. “The California condor had only about ten individuals left in zoos at the end of the 1980s, when it was reintroduced into the wild. There are now 500 in the wild. »