December 31, 2009 | 11
The deadly, contagious cancer that puts Tasmanian devils (Sarcophilus harrisii) at risk of extinction may have originated in another species, according to research published Thursday in the journal Science.
The cancer, known as devil facial tumor disease (DFTD), has wiped out nearly 70 percent of the world’s Tasmanian devils in the past 10 years. Once DFTD infects a devil, the cancer destroys the animal’s mouth, filling it with tumors that make it impossible for the animal to eat. Starvation and death follow within three to six months. Transmission is easy, because devils frequently bite one another on the mouth during mating or while fighting for territory.
Until now, scientists have had few, if any, clues to the origins of DFTD. But the new research indicates that the cancer may have actually attached itself to the Tasmanian devils, perhaps via their prey, as a kind of parasite.
The researchers behind this discovery sampled 25 different DFTD tumors from all over the Australian island of Tasmania (the only place that devils live in the wild). After sequencing the tumors’ genes, the team found that the growths were all genetically distinct from the devils themselves, but otherwise essentially identical to one another. In other words, the malignancies do not have the same DNA as the animals they are killing.
Meanwhile, the sequencing found that DFTD originates in Schwann cells, which are vital to the peripheral nervous system, and that a particular protein, periaxin, which is expressed by these cells, was also present in every tumor. According to lead researcher Elizabeth Murchison of Cold Spring Harbor Laboratory in Long Island, N.Y., the presence of periaxin could be used to diagnose DFTD before symptoms begin to display, an important step in quarantining disease-free devils to maintain a healthy population. It could also, possibly, be exploited to try to find a cure for the disease.
Other mutations of periaxin have been linked to forms of Charcot-Marie-Tooth disease. Guillain-Barré syndrome is also caused by Schwann cell malfunctions.
Murchison, a native of Tasmania, earlier this year received a L’Oréal-UNESCO UK and Ireland for Women in Science Fellowship for her work with DFTD and another transmissible cancer known as canine transmissible venereal tumor.
Image: Tasmanian devil infested with devil facial tumor disease, via Wikimedia Commons
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