Zoos are a research treasure, a Cell paper shows.
Humans and chimpanzees have nearly identical genes. But we use those genes differently, in part because of changes in gene-regulating regions such as promoters, which are close to genes they control, and enhancers, which can be hundreds of bases away. A Cell paper from UK and US researchers with a Danish collaborator found that enhancers, in particular, might drive mammalian diversity.
The scientists tracked the evolution of promoters and enhancers in 20 species—including humans, whales, and Tasmanian devils—using the ChIP-seq method. Chromatin immunoprecipitation collected DNA bound to proteins known to be at promoters and enhancers. Sequencing and aligning the DNA identified similar and divergent promoters and enhancers across the 20 species.
“It was pure basic research to see what part of the regulatory genome is evolving,” says study coauthor Mads F. Bertelsen, veterinarian at the Center for Zoo and Wild Animal Health, Copenhagen Zoo and University of Copenhagen affiliate professor.
The study found that in mammals, promoters generally evolve slowly and enhancers evolve rapidly. Recently evolved enhancers are implicated in adaptation since they are linked to positively selected genes. Enhancers, say the authors, are part of the “functional instructions” for mammalian diversity.
About the devils
Bertelsen joined the project to broaden the range of studied mammals: The Copenhagen Zoo is the only place in Europe that can provide samples from Tasmanian devils, which the zoo has because Denmark’s Crown Princess Mary is from Tasmania. The endangered animals are just one example of the enormous biodiversity available at zoos.
“Zoos are not just for showing animals to the public,” says Bertelsen. “They are also for education and research.” PhD students funded at the Copenhagen Zoo by the Alfred Benzon Foundation, among other organizations, work on projects as diverse as the animals. A study supported by the Danish Heart Association began by exploring why giraffes, who have high blood pressure to pump blood to their heads, don’t have pathologies associated with this condition in humans. The work expanded to study giraffe diet and physiology. Another student is studying co-evolution of microbes and hosts, relying on the tremendous variety in the microbiomes of zoo animals.
Zoo scientists can bring new research ideas to multidisciplinary life science teams, including that snake hearts shrink and grow as they feed and fast, elephants rarely get neoplasms, and some lizards carry Salmonella without getting sick. Zoos are most interested in collaborations that yield practical results for their animals, but Bertelsen says they also want to contribute to science in general. “The diverse species at zoos are a unique resource,” he says. “We have an obligation to make this resource available to research.
Reference: Villar D, Berthelot C, Aldridge S, Rayner TF, Lukk M, Pignatelli M, Park TJ, Deaville R, Erichsen JT, Jasinska AJ, Turner JMA, Bertelsen MF, Murchison EP, Flicek P, Odom DT. Enhancer Evolution across 20 Mammalian Species. Cell 2015; 60: 554–566.