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January 3rd, 2010:

More Details on Transmissible Cancer of the Tasmanian Devils

Tasmanian Devil photo: Debbi Long, flickr (click to see photo in original context)

I’ve previously mentioned the disease striking the Tasmanian Devils in a post on genetic bottlenecks:

Even less fortunate are the tasmanian devils who have so little genetic diversity that they are being decimated by a transmissible cancer. After fighting with an infected devil, which has tumors on its face and neck, tiny bits of the cancer will get into an uninfected devil’s wounds, and since the immune system can’t distinguish the foreign cancer cells from the devil’s own cells, the cancer cells reproduce unchecked, the trait that makes normal cancers, produced by mutated versions of our own cells, so deadly. And the solution mentioned in the article, to save the species by protecting 200 individuals, while better than letting them all die, will sacrifice even more genetic variability by subjecting the already inbred devils to a new population (and genetic) bottleneck.

Well now we know even more about the original of the cancer cells responsible for “Devil Facial Tumor Disease” (A truly frightening name). By studying the expression patterns of normal genes and microRNAs, a group of researchers have confirmed once and for all that the cancer cells really are being transmitted from one devil to another because the genes they looked at were identical in sequence in cancer cells taken from 25 different devils. The researchers place the original of the cancer as a more regular (mutation induced) cancer that arose in Tasmanian Devil living approximately two decades ago and even believe that they can identify that first mutated cell as a Schwann cell*. (more…)