Extinction Corporation sets its next (first?) target: Tasmanian tigers

Of all the species that humanity has wiped off the face of the Earth, the Tasmanian tiger is perhaps the most tragic loss. A wolf-sized marsupial sometimes called the Tasmanian tiger, this tiger met its end in part because the government paid its citizens a bounty for every animal killed. This ending came late enough that we have photos and movie clips of the last larval tiger ending their days in zoos. Late enough, in just a few decades, countries will start writing laws to prevent other species from seeing the same fate.

On Tuesday, a company called Colossal, which has already said it wants to bring the mammoth back, announced a partnership with an Australian laboratory that it says will eradicate the Tasmanian tiger with the goal of reintroducing them into the wild. A number of features of marsupial biology make this a more realistic target than mammoths, although there is still a lot of work to be done before we begin the debate about whether reintroducing the species is a good idea.

To find out more about the company’s plans for Tasmanian tigers, we had a chat with Colossal founder, Ben Lamm, and head of the lab he’s partnering with, Andrew Pask.


To some extent, Colossal is a way to organize and finance the ideas of Lam’s partner, George Church. Church has been talking about the eradication of mammoths for a number of years, spurred in part by advances in gene editing. The company is organized as a startup, and Lam said it is very open to commercializing the technology it develops while achieving its goals. “On our way to de-extinction, Colossal is developing new software, wet software, and innovative device technologies that could have profound impacts on both conservation and human health care,” he told Ars. But fundamentally, it’s about developing products that clearly don’t have a market: the ones that no longer exist.

Its general approach paint for mammoths Clear and straightforward, even if the details are very complex. There are so many mammoth tissue samples from which we can obtain at least partial genomes, which can then be compared to their closest relatives, the elephants, to find the main differences characteristic of the mammoth subspecies. Thanks to the gene-editing technology, key differences in the elephant stem cell genome can be modified, which essentially serve to “spur” elephant cells. After a bit of artificial insemination, we’ll have a shaggy beast ready for the arctic plains.

Again, details matter. At the beginning of the plan, we had not made stem cells for elephants, nor had we modified the genes even at a fraction of the desired size. There are credible arguments that the characteristics of the elephant’s reproductive system make a “small part of artificial insemination” that needs practical impossibility; If this occurs, it will take approximately two years for pregnancy to occur before the results can be evaluated. Elephants are also intelligent social creatures, and there is reasonable debate as to whether using them to this end is appropriate.

Given these challenges, it may not be a coincidence that Lamm says the Colossal was looking for another species to become extinct. Their research showed a project that was taking an almost identical approach: Integrated Genomic Restoration Research Laboratory for Tasmanian Tigers (TIGRR), based at the University of Melbourne and chaired by Andrew Pask.

in The Bag

As with the giant Colossal plans, TIGRR intends to obtain the genomes of Thylacine, and to identify key differences between this genome and related (mostly) lineages. dribbling), and then edit these differences into follicular stem cells, which will then be used for IVF. It also faces some major hurdles, as no one has yet made follicular stem cells, and no one has ever cloned marsupials – two things that have been done at least in placental mammals (albeit not fascioliasis).

But Baske and Lamm point out a number of ways in which the Tasmanian tiger is a more traceable system than the mammoth. First, the animal’s survival into recent years means there are plenty of museum specimens, so Baske says we’ll likely have enough genomes to understand a population’s genetic diversity — critical if we are to re-establish stable breeding.

Marsupial reproduction makes things easier, too. Bask told Ars that the marsupial fetus “puts in much lower nutritional demand when the point of birth is reached.” “The placenta doesn’t really invade the uterus.” Marsupials are also born about halfway through the embryonic development path of mammals. The rest of the development takes place in the mother’s pouch. In contrast to the in the womb Mammoths need years, Tasmanian tigers may need only a few weeks. Marsupial fetuses are also so small at birth that adoptive mothers can be much smaller than thylacine; Bask said his group plans to work with A Donart fat tailwhich is about the size of a small mouse.

Even after birth, Tasmanian tigers can be housed in a Donnert pouch for a short time, and Lam is excited about the prospect of developing an artificial pouch to move the animals from there to the point where they can be hand-bred. If not, some large marsupials can act as adoptive parents.

The dunnart is not the perfect replacement, as its lineage diverged from that of the Tasmanian tiger several million years ago (compared to less than a million for mammoths and elephants). This means that more genome editing must be done in order to dunnart the cells to bring them to a thylacine-like state. This is one reason why Bask is excited about the opportunity to collaborate with Colossal, which is developing methods for high-throughput genome editing.

None of this means that Tasmanian tigers are more or less likely to be revived. Colossal will still have challenges in identifying the changes that are absolutely necessary to produce a thylacine, and any other changes that are required to ensure that the genome survives with all of that class of changes (these compensatory mutations It could be necessary to allow a species to survive through evolutionary changes). However, most of the risks involved appear to be more manageable in her case.

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