With added thylacine: The picture shows a two-week old mouse foetus. The colour indicates the expression of the functioning thylacine Col2A1 promoter in the developing cartilage of the mouse.

Credit: Andrew Pask / University of Melbourne

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SYDNEY: DNA from the extinct Tasmanian tiger has been successfully extracted and used to resurrect a functioning version of a gene fragment in a mouse, Australian scientists have announced.

This is the first time anyone has been able to transfer genetic material from an extinct species into a living animal. Previously, scientists have recovered and analysed genes from extinct species – such as mammoths and Neanderthals – and predicted their functions.

"This is the first time that DNA from an extinct species has been used to induce a functional response in another living organism," said Andrew Pask, a zoologist at the University of Melbourne and lead author of a report detailing the discovery in the journal PloS One today.

"Restored to life"

The last known Tasmanian tiger (Thylacinus cynocephalus) died in Hobart Zoo in 1936. Since then, the animal has captured the imagination of scientists and public alike, with sporadic 'sightings' in the wild and occasional discussions among researchers about the possibility of bringing the species back. See early 20^th century video footage of the thylacine here.

Working with Marilyn Renfree, also at Melbourne, and Richard Behringer, a molecular geneticist at the University of Texas in Austin, USA, Pask extracted the fragmented DNA of a region of code called a collagen promoter.

To collect enough DNA for a complete promoter, they had to extract genetic material from three pouch young preserved in ethanol, and one adult pelt. These thylacine specimens were collected in Tasmania over 100 years ago and are kept in the collections of Museum Victoria in Melbourne.

The team then pieced together and amplified the DNA for the promoter, called Col2a1, and injected it into mouse embryos. In all mammals, including mice and thylacines, the promoter (not a gene as such) aids the production of collagen for the skeleton of the developing embryo. Pask's team added a gene that creates blue dye to the end of the DNA so they could tell in which parts of the developing mouse embryos it had been expressed.

As detail in their paper, they found that the collagen promoter was expressed throughout the skeletal system of the developing mice and behaved in much the same way as the normal mouse version.

"We have restored to life the genetic potential of a fragment of this extinct mammalian genome," write the authors. "For those species that have become extinct access to their genetic biodiversity may not be completely lost."

Tweaking a Tasmanian devil

"This is really exciting science," commented Hamish MacCallum, an expert on marsupial carnivores at the University of Tasmania in Hobart. "It offers the prospect of better understanding the function of genes in extinct animals."

However, he noted that the discovery is unlikely to take us any closer to resurrecting an entire thylacine: "This is just one small gene fragment, expressed in an embryonic mouse. How many genes the thylacine had is unknown but could be in the region of 30,000 - given what we know about the human genome."

Neither would recreating the thylacine "be a matter of just tweaking a few genes in a Tasmanian devil embryo," added MacCallum. "Thylacines were in a different family from all the other marsupial carnivores, so the genetic composition would be very different."

Swansong: Some of the last thylacines pictured here at Hobart Zoo in the early 1900s (Credit: Tasmanian Museum and Art Gallery).

Jeremy Austin, of the Australian Centre for Ancient DNA at the University of Adelaide, said that the discovery "is significant in that the authors have managed to express part of the genome of an extinct species in a living organism." However, he argued that similar studies have extracted genes from animals, such as mammoths, that are many thousands of years older – and the genes have given us interesting information about those animals, such as coat colour.

"Most people are going to be very interested in this story," said Austin. "But what does it tell us about thylacines?"

More informative genes

Pask countered that insertion of the collagen promoter DNA is meant as a proof of principle. His team are now planning to insert genes that will tell us something new about the extinct marsupial.

"Now that we know we can get genes from this extinct animal, we can go back and look at much more interesting thylacine genes that are not present in other animals, and discover their funtions too," said Pask.

The genes he is most interested in are part of the so-called HOX cluster responsible for encoding the basic body plan of all animals from fruit flies to elephants. "The thylacine has a very unique body plan and it would be interesting to look at the early embryonic development of this," said Pask. The convergent similarity between the marsupial thylacine and the eutherian mammal dog has long fascinated scientists.

"As Australians we feel pretty bad about the recent extinction of the thylacine," said Pask. "It would be great to go back and understand a little more about its biology."