Extinct Genes Resurrected

Tasmanian tiger Tasmanian Museum and Art Gallery

Friday, May 23rd, 2008--

Researchers from the University of Melbourne in Australia and the University of Texas extracted DNA from preserved samples of the now-extinct Tasmanian tiger (Thylacinus cynocephalus) and mixed it into a living organism. The genetic hybrid is mostly mouse: it contains only one Tasmanian tiger gene--Col2A1, which codes for skeleton formation. But this the first time that researchers have been able to resurrect DNA from an extinct animal and watch it function in a living animal. The results are reported in the journal PLoS ONE this week.

"We were very surprised that it worked," says Andrew Pask, RD Wright Research Fellow in the zoology department at the University of Melbourne in Australia and author on the study. After all, a mouse and a Tasmanian tiger--which is a marsupial--are not close relatives: they last shared a common ancestor about 130 million years ago, Pask says. What this study shows, he says, is "the potential for looking at even quite distantly-related species in a mouse in order to gain a deeper appreciation of the genetics of extinct species."

The last known Tasmanian tiger died in 1936 in the Hobart Zoo in Tasmania, Australia. Pask and his colleagues extracted DNA from dried pelts and from tissues samples that had been preserved in alcohol. They obtained the samples from museum collections.

The researchers stitched the extinct gene together with a gene from bacteria that creates a blue pigment--allowing them to track whether the gene was functioning in the mouse. "Whenever the extinct gene is switched on, it produces a blue color. So all the parts of the embryo that are blue show exactly where that extinct gene is being expressed or switched on," Pask explains.

In past experiments, researchers have successfully isolated DNA from Neanderthals and mammoths and inserted them into cell cultures in the lab. "In our experiment we've actually taken the DNA and put it into a whole living organism." Pask says.

Pask plans to delve deeper into the Tasmanian tiger genome; the researchers are particularly interested in the genes that code for the marsupial's body pattern. "If you look just at the skeleton, it's almost impossible to tell it apart from the domestic dog," Pask says. Since the two species are distant relatives, one question is whether the genetic blueprints for the body are the same. Pask says: "We can compare those genes and see how the different genomes have evolved to have a body that looks so similar."

Pask says this experiment was a proof of concept. Now that the technique has been shown to work, Pask and his colleagues can begin looking for genes that may be unique to extinct animals--"so we can start to understand what it was that defines that as a species," he says.

--Flora Lichtman