For the first time, researchers have inserted the genetic material of an extinct animal into a living one. The finding shows how lost information about species from the past can be retrieved, and also provides a glimpse into how long-gone creatures may someday get a second chance at life.
"Now that we've shown you can do this, it opens up the floodgates for all kinds of extinct species," says Andrew Pask, a fellow in zoology at the University of Melbourne in Australia and lead author of a paper published in the online journal PLoS ONE. The gene that the scientists activated in mouse fetuses contained instructions that helped produce cartilage in the rodent's developing skeleton.
The Tasmanian tiger DNA came from specimens that had been preserved in a museum for over a century. The researchers selected a gene called Col2a1 that is possessed by many vertebrates, ranging from mice to people. By attaching a marker to the Tasmanian tiger's version of Col2a1 that glows blue when stained by a chemical, scientists were able to see where the mouse's body had expressed the gene of the departed beast.
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"We saw the genetic information of an extinct animal get read out into a blue pattern," says co-author Richard Behringer, a professor of molecular genetics at the University of Texas M.D. Anderson Cancer Center in Houston.
Earlier studies on plant and animal genomes have already yielded useful data, Pask says, pointing to some of surprises found in the platypus genome unveiled just a few weeks ago. Among them: novel antimicrobial genes that could lead to new antibiotics as well as insight into the origin of descended testicles in mammals.
Previous work had allowed scientists to "read" the genetic codes of extinct life forms, but Pask's method tests for the actual function of genes. "We can now access extinct species' genes and see if there is something interesting," Pask says. Other researchers have isolated DNA from woolly mammoths and even Neandertals, and will likely apply the technique to try to glean unique information from erstwhile inhabitants of the planet.
Tasmanian tigers were wolf like mammals with striped backs that were hunted to extinction in Australia and on the Pacific island off its southeastern coast for which the tiger is named. Their demise has haunted many Australians, including study co-author Marilyn Renfree. "We feel a bit guilty about the ancestors of ours who hunted this wonderful carnivore to extinction," says Renfree, a professor of zoology and colleague of Pask's at the University of Melbourne. The last known Tasmanian tiger in the world died due to exposure on a cold night in the Hobart Zoo in Tasmania's largest city in 1936.
As a marsupial (a mammal that rears its babies in a pouch outside the womb), the Tasmanian tiger is actually more closely related to a kangaroo than a cat, or even a canine, which it closely resembles. The researchers plan to analyze genes that gave Tasmanian tigers their distinct traits, such as stripes and gaping jaws. The prospects of ever bringing back the Tasmanian tiger, however, remain extremely slim.
"In our work thus far, we have looked at one gene, and we're going gene by gene," says Behringer. Most living beings contain thousands of genes that interact in very complex ways, making a full-fledged resurrection virtually impossible. "But as long as you have the DNA of a species, then you can get that information," Behringer says.
Renfree adds: "We made one tiny step forward by looking at the function of one gene, but you never know what will be possible someday."