dendroica:Tasmanian devils are evolving resistance to their devastating contagious cancers - The Was
dendroica:Tasmanian devils are evolving resistance to their devastating contagious cancers - The Washington PostBut at long last (and probably just in the nick of time) the devils are starting to put up a fight. In a study in the journal Nature Communications, scientists report that they’ve found new variants in parts of the Tasmanian devil genome associated with the immune system and cancer response — proof, these scientists believe, that the creatures are evolving resistance to the fast-moving disease.Andrew Storfer, an evolutionary geneticist at Washington State University and a co-author on the study, had been following the sad case of the Tasmanian devils for years. He’d seen images of the creatures, which are the size of a pekingese and have the ferocity of a pit bull, covered in painful red tumors. He’d also read the studies predicting local extinction of some populations in a matter of years. Strangely, some of those populations still persisted, despite the epidemiological models that predicted otherwise.“At that point, our hypothesis was maybe there was evolution,” Storfer said. “The challenge, of course, was finding evidence in the genome.”Luckily, scientists have been taking DNA samples of Tasmanian devils for decades — long before the current DFTD outbreak. Storfer and his colleagues were able to gather up the genomes of more than 250 individuals, quickly sequence relevant sections, and compare their samples to figure out where they differed.Tasmanian devils have very little genetic diversity among them, because their population has been through several bottlenecks — periods when a sharp decline in population left just a small number of Tasmanian devils to spawn the next generation. This lack of diversity may have contributed to the weakness of their immune systems. If Tasmanian devils had evolved resistance to the cancer that ravages them, Storfer and his colleagues might find evidence of gene variants that didn’t exist before the outbreak.They found exactly what they were looking for: two regions of the genome, both associated with immune function and cancer response, where devils from affected communities had variants that didn’t exist in the pre-outbreak population. Further study of the particular genes involved could help explain why DFTD is so deadly and how we might help animals without these gene variants resist the disease.“We’re going to see if the favored alleles are actually conferring longer duration of survival” — i.e., keeping infected devils alive long enough to reproduce — “or more offspring. I don’t know necessarily they would provide complete resistance but they could be more related to resistance once infected,” Storfer said. “That’s going to help us understand how much damage individuals get, how fast that damage is, and how they survive.”People often ask Storfer if he believes the devils will go extinct soon. He said no — “this result leads me to be optimistic.” -- source link