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Tas­man­ian dev­ils evolve to resist deadly trans­mis­si­ble facial cancer

pub­lished 19 Octo­ber 2016 | mod­i­fied 19 Octo­ber 2016

Tasmanian devil with facial cancerTas­man­ian dev­ils are evolv­ing in response to a highly lethal and con­ta­gious form of can­cer, a Wash­ing­ton State Uni­ver­sity (WSU) researcher has found.

Andrew Stor­fer, WSU pro­fes­sor of biol­ogy, and an inter­na­tional team of sci­en­tists dis­cov­ered that two regions in the genomes of Australia’s iconic mar­su­pi­als are chang­ing in response to the rapid spread of devil facial tumour dis­ease (DFTD), a nearly 100 per­cent fatal and trans­mis­si­ble can­cer first detected in 1996.

The work, pub­lished online on 30 August in Nature Com­mu­ni­ca­tions, sug­gests some Tas­man­ian devil pop­u­la­tions are evolv­ing genetic resis­tance to DFTD that could help the species avoid extinc­tion. Addi­tion­ally, the genomic data will sup­port future med­ical research explor­ing how ani­mals evolve rapidly in response to can­cer and other pathogens.

Our study sug­gests hope for the sur­vival of the Tas­man­ian devil in the face of this dev­as­tat­ing disease
Andrew Stor­fer, co-​author, pro­fes­sor of biol­ogy, Wash­ing­ton State University »

Ulti­mately, it may also help direct future research address­ing impor­tant ques­tions about the evo­lu­tion of can­cer trans­mis­si­bil­ity and what causes remis­sion and reoc­cur­rence in can­cer and other dis­eases,” Stor­fer said.

Dis­ease kills 80 per­cent
Tas­man­ian dev­ils are the largest car­niv­o­rous mar­su­pi­als in the world and an inte­gral part of Australia’s nat­ural her­itage. Dev­ils dis­play sig­nif­i­cant aggres­sion toward one another, which often involves bit­ing on the face. This some­times trans­mits DFTD, one of only three known forms of trans­mis­si­ble can­cer and by far the most deadly.

Twenty years since its dis­cov­ery, DFTD has wiped out an esti­mated 80 per­cent of dev­ils in Tas­ma­nia, the only place in the world where the ani­mals live.

By com­par­i­son, canine trans­mis­si­ble vene­real tumour, a sex­u­ally trans­mit­ted form of can­cer that only affects dogs, has been around for at least 11,000 years and is gen­er­ally not fatal to domes­ti­cated animals.

Col­lec­tions offer unique research oppor­tu­nity
Despite mod­els that pre­dicted extinc­tion, pop­u­la­tions of Tas­man­ian dev­ils at long-​diseased sites per­sist. Stor­fer, an evo­lu­tion­ary geneti­cist who has stud­ied DFTD for nearly a decade, teamed up with col­leagues in the United States, Great Britain and Aus­tralia to inves­ti­gate whether there was a genetic com­po­nent to some of the dev­ils’ survival.

If a dis­ease comes in and knocks out 90 per­cent of the indi­vid­u­als, you might pre­dict the 10 per­cent who sur­vive are some­how genet­i­cally dif­fer­ent,” said study co-​author Paul Hohen­lohe, assis­tant pro­fes­sor of biol­ogy at the Uni­ver­sity of Idaho. “What we were look­ing for were the parts of the genome that show that difference.”

The researchers mined a vast trove of devil DNA col­lected and stored before and after the out­break of DFTD by wildlife ecol­o­gist and asso­ciate pro­fes­sor Menna Jones, study co-​author, and her research team at the Uni­ver­sity of Tasmania.

Hope­ful of breed­ing resis­tant dev­ils
The fre­quency of genes in spe­cific regions of the old DNA were com­pared to the fre­quency of genes in cor­re­spond­ing regions of DNA col­lected fol­low­ing DFTD emer­gence at three sites on Tasmania.

Stor­fer and col­leagues iden­ti­fied two small genomic regions in the DNA sam­ples from all three sites that exhib­ited sig­nif­i­cant changes in response to the strong selec­tion imposed by the dis­ease. Five of seven genes in the two regions were related to can­cer or immune func­tion in other mam­mals, sug­gest­ing that Tas­man­ian dev­ils are indeed evolv­ing resis­tance to DFTD.

The researchers are in the process of deter­min­ing the spe­cific func­tion­al­ity of the genomic regions iden­ti­fied in the study.

The researchers are hope­ful that dis­ease free Tas­man­ian dev­ils with the appar­ently DFTD resis­tant DNA can be bred to enhance the genetic diver­sity of an off-​island cap­tive insur­ance pop­u­la­tion in case devil rein­tro­duc­tions are needed in the future.

(Source: Wash­ing­ton State Uni­ver­sity press release, 30.08.2016)

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