Nine Steps to Thylacine
Australian Marsupial wolf: return from oblivion?
The "return from the dead", or rather from the extinct, in the application to animal species has not yet become a reality, but it is already close to it. And one of the first such "returnees" may be the thylacine, an Australian marsupial wolf that disappeared from the face of the earth about a hundred years ago. The work program is described in the article The 9 steps to de-extinction Australia's thylacine on the website of the University of Melbourne.
The number of marsupial species, the most famous of which are kangaroos, is slowly but steadily declining. Today, they have been preserved almost exclusively on the Australian continent, and prolonged isolation has led to a decrease in genetic diversity and the ability to adapt to sudden environmental changes. So, in principle, it is not difficult to "finish off" such a species, and human activity, among other things, can contribute to this.
Once the typical inhabitants of Australia were marsupial wolves, or thylacines (Thylacinus cynocephalus), but already about 3 thousand years ago they were found only on the island of Tasmania. In the XIX century. immigrants from Europe began to hunt these predators en masse, which became a threat to poultry houses and sheep flocks. As a result, the last known representative of the marsupial wolves died in 1936 in a private zoo in Hobart, the capital of Tasmania.
The last thylacine in Hobart Zoo. 1933
The adult thylacine reached 180 cm from the nose to the tip of the tail, and it was often described as a long striped dog. This marsupial Australian predator, standing at the top of the food pyramid, once played an important role in stabilizing the ecosystems of this continent. Now this role has been transferred to the second-feral dogs dingoes and crocodiles, but their "competencies" in this area are clearly not enough.
The same thylacines could, for example, be removed from the population of sick Tasmanian devils in time. And this would allow us to keep control over the spread of deadly infectious cancer among the latter, which is why these animals are on the verge of extinction. And if the marsupial wolves returned, they could easily occupy their ecological niche, because the nature of Tasmania has changed little over the past centuries...
Scientists from the University of Melbourne (Australia) have been working on the task of returning thylacine for a long time. As part of this project, the genome of this predator was decoded in 2017, and later the genomes of several living closely related species, including the Tasmanian devil and the fat-tailed marsupial mouse (fat-tailed dunnart).
It is assumed that the cells of these marsupials can become the "progenitors" of thylacine cells, for which their DNA will have to undergo genomic editing.
Now the main task of researchers is to use bioinformatic methods to compare the genomes of potential "candidates" for thylacine in order to find specific areas that need to be edited based on its genetic data. Work is also underway with the stem cells of the marsupial mouse, which has become a model object for testing molecular biological methods taking into account the characteristics of marsupials. All these methods will be useful not only for the revival of thylacine, but also for solving the problem of preserving biodiversity in populations of marsupial species at risk.
The next step will be the development of assisted reproductive technologies suitable for these animals, which are needed to create an embryo from stem cells and transfer it to the uterus of a surrogate mother.
The fact is that, unlike placental animals, marsupial embryos can, apparently, be planted in females of many closely related species. Moreover, a surrogate mother may not be needed at all. Since the pregnancy of marsupials lasts very short, tiny cubs continue to develop in the mother's pouch, where they feed on milk. An alternative may be artificial feeding – so scientists will be able to grow the fetus completely "in vitro".
According to researchers, the work on the restoration of marsupial wolves will take at least a decade. One can argue about the ethics of such developments and the problems of returning an extinct species to nature, but in any case, technological advances in the field of marsupial biology will be useful for creating a biobank of these animals, which is important for preserving their diversity. In particular, marsupial genome editing technologies can be used to give vulnerable animal species resistance to the toxin of the cane toad, introduced in 1935 to control pests on sugar plantations and which has become a real disaster for the continent.
Such studies will help to understand the genetic basis of species extinction. And the development of reproductive technologies will increase the chances of survival of rare endemic species – unique "evidence" of the evolution of life on the planet.
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