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article imageTasmanian Devil's genes evolving — Becoming resistant to cancer

By Karen Graham     Aug 31, 2016 in Science
In what is being called a "rapid evolutionary response," Australia's Tasmanian devils are developing resistance to the Devil facial tumor disease (DFTD), according to a new study.
Tasmanian devil facial tumor disease is one of only four cancers known to be transmissible, including forms have been identified in dogs, soft-shell clams, and Syrian hamsters. DFTD was first recorded in 1996, and since that time DFTD has wiped out nearly 80 percent of the dog-sized carnivorous marsupials.
An international group of researchers made up of scientists from the U.S., U.K., and Australia, described their findings in the journal Nature Communications, published on August 30.. They looked at 10,000 tissue samples from 294 devils, covering three different populations that included data from before and after the disease was first recorded in 1996, and up through 2014.
The three focal populations are labelled and marked with large magenta circles. The magenta lines in...
The three focal populations are labelled and marked with large magenta circles. The magenta lines indicate the approximate location of the disease front in 2000, 2005, 2010 and 2015.
Epstein, B. et al.
In sequencing the Tasmanian devil's genome, the team found seven different genes in two parts of the genome that seemed to be related to immune response or cancer risk in humans. All seven genes appeared to have similar selection signatures across the populations in the three areas studied.
"We characterized about 800,000 locations across the genome of each individual Tasmanian devil," said Dr. Hohenlohe, an evolutionary biologist at the University of Idaho, according to the BBC.
"Our goal is to look for genetic variants that could convey some sort of resistance… so that it may be possible to manage captive populations to ensure that that genetic variation is maintained."
The researchers found that two sections of the devil's DNA were under "acute selection pressure." What turned out to be amazing was that the genes in the two sections were changing faster than the rest of the genome. The specific variations in those changing genes were found in all three populations, reports ABC.net.au.
The seven candidate genes found in or closest to regions with concordant signatures of selection.
The seven candidate genes found in or closest to regions with concordant signatures of selection.
Epstein, B. et al.
"Particularly, there are several that seem to be involved in directing immune cells to dysfunctional cells or pathogens, and we think those are particularly promising," said lead author Dr. Brendan Epstein from Washington State University.
What is particularly exciting about the study is that we are witnessing an evolutionary change that has come about in only six generations, a relatively short period of time. Many of the animals studied should have already been dead from their disease, but they are still alive.
Dr. David Rollinson is a biologist at the Natural History Museum in London and specializes in genetics. He says the study is "quite impressive," and is a real example of natural selection in action. "I find it quite exciting," Dr. Rollinson told the BBC. "There's been great concern that the Tasmanian devils may be wiped out by this strange, transmissible cancer."
More about tasmanian devils, transmissible cancer, Evolution, genetic response, immune modulated resistance
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