Decoding Endangered Tasmanian Devil Genome

Completing the genome sequence of the endangered Tasmanian devil may help save it.

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By Kirsten Weir, ISNS Contributor

(ISNS)—The Tasmanian devil is known for its powerful jaws, frightening screeches and foul temper. Lately, though, it has earned a more dubious claim to fame: A strange and devastating disease is ravaging its population, pushing the world's largest meat-eating marsupials to the edge of extinction.

Now, an international team of scientists has sequenced the Tasmanian devil genome. The results of their study appear this week in the Proceedings of the National Academy of Sciences.

Tasmanian devils once roamed Australia, but died out across most of their territory at least 400 years ago, probably due to changing local weather conditions and the spread of the dingo. Today the creatures survive only on the south Australian island of Tasmania—for now. Since 1996, a new disease has decimated the devil population. As a result, Australia deemed the devil an endangered species in 2008.

Known as DFTD, devil facial tumor disease causes cancerous tumors to sprout on the animals' mouths and heads. DFTD is no ordinary cancer. Unlike almost all other forms of cancer, DFTD is highly contagious. Deadly tumor cells are passed from animal to animal when they come together to mate or fight.

Over the last 15 years the disease has spread across Tasmania. In the hardest-hit areas it has claimed as much as 90 percent of the devil population, according to Australian government estimates.

"If nothing is done, the species will easily be wiped out within the next 10 years," said Stephan Schuster, a professor of biochemistry and molecular biology at Penn State University and a co-author of the new study.

Schuster and colleagues deciphered the full genomes of two Tasmanian devils: a female that contracted DFTD in the wild, and a male that proved resistant to two strains of the cancer before dying from a third strain last year.

The researchers also reviewed the DNA of 175 other devils to find out how much variation exists from animal to animal. They confirmed that genetic diversity was extremely low.

"They're highly inbred," said Webb Miller, co-author of the study and professor of biology and computer science engineering at Penn State.

That makes it all the more important to get a handle on the devils' genetic heritage, he said. The Australian government has already begun breeding healthy devils in captivity, keeping them in "protective custody" while the disease burns through the wild population.

"Once there are no more carriers in the wild, you could repopulate Tasmania from this breeding stock," Schuster said.

But instead of randomly choosing animals for protective custody, Schuster and Miller say, conservationists should test animals' genes to ensure the captive population contains as much diversity as possible.

The more genetic diversity there is in the population, Miller said, the better the animals will withstand new diseases and other new threats in the future.

George Amato, a conservation geneticist at the American Museum of Natural History, notes that it's not necessary to sequence an entire genome to preserve genetic diversity.

Identifying key gene sequences—rather than decoding the entire DNA of an endangered species—is typically a better use of conservation dollars, Amato said.

"Just because you can sequence a whole genome doesn't mean you should," Amato said.

On the other hand, Amato said, the Tasmanian devil and its bizarre cancer are a special case. Having its entire genome sequence will be valuable for scientists working to understand DFTD.

In fact, Miller said, his team has already identified spots on the genome that might be involved in resistance to DFTD. "We have lots of clues," he said.  

Genetics offers a powerful tool for understanding endangered animals and preserving their diversity.

"In almost every case in conservation, there's an important role for genetics," Amato said.

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