Disinterested Affection: Dogs, Humans and Evolution: Domesticated dogs, genomes, and malaria

Wednesday, December 20, 2017

Domesticated dogs, genomes, and malaria

Plasmodium falciparum is a unicelluar protozoan parasite of humans and the deadliest species of Plasmodium. It is transmitted through the bite of a female Anopheles mosquito and responsible for Therefore it is regarded as the deadliest parasite in humans, causing at least one million deaths every year. The species evolved about 10,000 years ago from the malarial parasite found in gorillas. A World Health Organization report in 2015, suggested there were 214 million cases of malaria worldwide.

Dogs spread across the globe with humans and have had to adapt to the same environmental conditions as humans. A Chinese research team led by Zhang has successfully identified genes selected in African dogs and functionally verified the action of one of these as the first evidence of dog adaptation to malaria.

“Recently, we have shown the first evidence that dogs can undergo similar adaptations as humans, using the same genes to live in the high altitudes of Tibet,” said professor Ya-Ping Zhang.

“Dogs have survived in tropical environments for thousands of years alongside humans,” said Zhang. “In this study, we have identified genes associated with insulin secretion and sensitivity, immunity, angiogenesis and ultraviolet protection showed adaptive selection.”

Yan-Hu Liu et al. (2017) sequenced the genomes of 19 dogs from Nigeria. For this new data set, they identified a set of candidate genes for natural selection in African village dogs and also carried out functional studies to confirm that one of these, ADGRE1, might be responsible for providing host immunity to Plasmodium infection—a target of selection associated with malaria.

“Our study suggests ADGRE1 also contributes to defense against Plasmodium infection in dogs, and thus, convergent evolution in this gene between humans and dogs,” said Guo-Dong Wang. “This is a novel finding since in earlier studies the most apparent cases of convergent evolution between humans and dogs were in genes for digestion and metabolism, neurological process, and cancer.”

The authors went on to show in cell culture experiments in the lab that the derived variant of ADGRE1 is linked to increased phagocytosis in cells infected with Plasmodium parasites, making it very likely that the ADGRE1 confers protection against Plasmodium infection by stimulating the immune response against the parasite.

In addition, they investigated the Nigerian dogs’ demographic history in relation to other dogs, including Eurasian gray wolves and African golden wolves. They found that the Nigerian dog population diverged from Eurasian dog populations around 14,000 years ago. After this divergence, the population fell on hard times, and experienced a severe bottleneck (leading to a reduced genetic diversity within the Nigerian dog population) and also gene flow from African golden wolves after the divergence.

Finally, they explored signals of selection in the Nigerian dog samples, and identified a number of candidate genes that are also linked to dietary and environmental factors.

As the authors note, since ADGRE1 has also been implicated in an adaptive response to Plasmodium in humans, it makes for a nice genetic tale of dogs utilizing similar tricks from living alongside their human companions to adapt to new environments.

References

Caspermeyer J. 2017. Scientists Find Evidence Our Best Friends, Dogs, Similarly Adapted to Malaria in Africa, Molecular Biology and Evolution, msx289, https://doi.org/10.1093/molbev/msx289

Liu Y-H, Wang L, Xu T, Guo X, Li Y, Yin T-T, Yang H-C, Yang H, Adeola AC, Sanke OJ, et al. 2017. Whole-genome sequencing of African dogs provides insights into adaptations against tropical parasites. Molecular Biology and Evolution.

Advance Access published October 10, 2017, doi: 10.1093/molbev/msx258

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Tens of thousands of dogs are bitten each year by snakes. The USA has about 25 species of venomous snakes; they occur in all states except Alaska, Hawaii, and Maine. Learn what simple steps you can take to protect your dog from snake envenomation. Learn what to do if you or, your dog, is bitten by a venomous snake. If you hunt, fish, camp or hike with your dog in areas where poisonous snakes occur you will want the information in this book. If you live in an area with rattlesnakes, you will want the information in Dogs & Snakes, Avoiding the bite.

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This blog is about dogs, dog-human relationships, and my thoughts on the origins and the domestication of dogs. When I say my thoughts, it needs qualification because much of the writing is not the result of my original thinking, but of reading research and anecdotes about dogs and humans, studies of fossils and archeological remains, anatomy, DNA, and behavior. The posts will be documented in standard fashion with author and date, and the literature cited and references are listed on a reference page or at the bottom of the post. The title comes from William Youatts’ 1846 [1857 edition] book, The Dog. On page 14 he wrote, "The dog is the only animal that is capable of disinterested affection. He is the only one that regards the human being as his companion, and follows him as his friend; the only one that seems to possess a natural desire to be useful to him, or from a spontaneous impulse attaches himself to man." Youatt’s book is remarkably insightful for the mid-19th century; he opens Chapter 1 with a comment about dogs being the most intelligent animal other than humans; notes the emotional attachments dogs and humans form, including the sense of loss when dogs loose the humans they have bonded with; and supports the idea that dogs were descended from wolves. This is an idea that was rejected and re-accepted numerous times in the 19th and 20th centuries, and one that will be discussed here.

John C. Murphy

John C. Murphy is a retired science teacher and science administrator. His most recent book Secrets of the Snake Charmer examines what we have learned about snakes in the first decade of the 21st century. Previous books include Tales of Giant Snakes, Amphibians and Reptiles of Trinidad and Tobago, and Homalopsid Snakes, Evolution in the Mud. Current interests and projects include, numerous squamate systematic projects that focus on the Neotropics and aquatic snakes. His interests also have expanded to dogs and their evolution. He is an avid photographer and a research associate in Science & Education at the Field Museum in Chicago.