By Richard Macey
In a world first, scientists have extracted a gene from the extinct Tasmanian tiger and successfully inserted it into a mouse embryo.
It is the first time a gene from any extinct animal has been brought back to life inside another living creature.
However, the researchers, from the University of Melbourne and the University of Texas, say the technology will not lead to the cloning of an entire Tasmanian tiger, or thylacine.
"It's a nice dream to have, but it's probably not going to happen," said Marilyn Renfree, a University of Melbourne zoology professor and a member of the team.
However, the scientists say it may now be possible to reactivate genes taken from many extinct creatures, including dinosaurs and even the predecessors to modern humans, providing new insights into their biology.
Obtaining the thylacine gene, called Col2a1, was itself a major challenge, because DNA begins breaking down after death.
Professor Renfree and the project's team leader, Andrew Pask, also from the University of Melbourne's zoology department, managed to extract fragments of the gene from four 100-year-old thylacines - three pouch dwelling infants and the skin of one adult - preserved in ethanol at Museum Victoria.
The bits were combined to form a complete gene.
"Putting the pieces together is a bit like a jigsaw puzzle," said Dr Pask.
It was then genetically modified with the addition of a bacteria gene that produces a blue colour.
Professor Richard Behringer, deputy head of the Department of molecular Biology at the University of Texas, finally inserted the reassembled thylacine gene into a mouse embryo.
Cartilage in the developing bones of the embryonic mouse turned blue, signalling that the thylacine gene was working.
A similar gene is also responsible for developing cartilage in mice, so the experiment did not produce an embryo that was part mouse, part thylacine. "We were not trying to cause anything to switch on or off," said Professor Renfree.
Dr Pask said scientists were already able to study genes, taken from extinct animals, in test tubes. "We wanted to show it was possible to take a gene from an extinct animal and look at its function in a living animal."
Future experiments may be able to extract more specialised genes - such as those that were responsible for giving the thylacine its dog-like features, or its distinctly patterned skin, into a mouse.
"We might be able to produce a striped mouse," said Dr Pask, even one with a thylacine pouch.
"This has not been done for fun," said Professor Renfree. "It has been done to learn more about the biology of a creature that we, humans, made extinct."
Experimenting with genes from dinosaurs might reveal what their skin looked like, and resolve the debate about whether they were cold or warm blooded.
Genes from the fossils of Neanderthal man may provide clues to the modern human's evolution.
Dr Pask said that while he would like to think they had brought one microscopic part of a thylacine back to life, cloning an entire Tasmanian tiger would be immensely more complicated.
It would require recreating not just one gene, but 30,000 - which would all have to be reassembled correctly in chromosomal packages.
However, scientists should now be able to study extinct animals gene by gene, as long as they can find original DNA that has survived in fossils or museum specimen.
Their research has been published in the journal PLos One. See http://www.plosone.org/doi/pone.0002240