What makes dogs man's best friend?

June 27, 2018, University of Michigan
Credit: CC0 Public Domain

From pugs to labradoodles to huskies, dogs are our faithful companions. They live with us, play with us and even sleep with us. But how did a once nocturnal, fearsome wolf-like animal evolve over tens of thousands of years to become beloved members of our family? And what can dogs tell us about human health? Through the power of genomics, scientists have been comparing dog and wolf DNA to try and identify the genes involved in domestication.

Amanda Pendleton, Ph.D., a postdoctoral research fellow in the Michigan Medicine Department of Human Genetics, has been reviewing current domestication research and noticed something peculiar about the DNA of modern dogs: at some places it didn't appear to match DNA from ancient dogs. Pendleton and her colleagues in assistant professor Jeffrey Kidd, Ph.D.'s laboratory are working to understand the dog genome to answer questions in genome biology, evolution and disease.

"We convinced ourselves that previous studies found many genes not associated with being a dog but with being a breed dog," says Pendleton. Breed dogs, which mostly arose around 300 years ago, are not fully reflective of the genetic diversity in dogs around the world, she explains. Three-quarters of the world's dogs are so-called village dogs, who roam, scavenge for food near human populations and are able to mate freely. In order to get a fuller picture of the genetic changes at play in dog evolution, the team looked at 43 village dogs from places such as India, Portugal and Vietnam.

Armed with DNA from village dogs, ancient dogs found at burial sites from around 5,000 years ago, and wolves, they used statistical methods to tease out genetic changes that resulted from humans' first efforts at domestication from those associated with the development of specific breeds. This new genetic review revealed 246 candidate domestication sites, most of them identified for the first time by their lab.

Now that they'd identified the candidate genes the question remained: What do those genes do?

'A good entry point'

Upon closer inspection, the researchers noticed that these genes influenced brain function, development and behavior. Moreover, the genes they found appeared to support what is known as the neural crest hypothesis of domestication. "The neural crest hypothesis posits that the phenotypes we see in domesticated animals over and over again—floppy ears, changes to the jaw, coloration, tame behavior—can be explained by that act in a certain type of cell during development called neural crest cells, which are incredibly important and contribute to all kinds of adult tissues," explains Pendleton. Many of the genetic sites they identified contained genes that are active in the development and migration of neural crest cells.

One gene in particular stuck out, called RAI1, which was the study's highest ranked gene. In a different lab within the Department of Human Genetics, Michigan Medicine assistant professor of Shigeki Iwase, Ph.D., has been studying this gene's function and role in neurodevelopmental disorders. He notes that in humans, changes to the RAI1 gene result in one of two syndromes—Smith-Magensis syndrome if RAI1 is missing or Potocki-Lupski syndrome if RAI1 is duplicated.

"RAI1 is a good entry point into studying brain function because its mutation results in a brain disorder," he says. "Studies suggest that this protein controls the expression of several genes involved in circadian rhythms. One of the unique features in these conditions is the problem these patients have with sleep." In dogs, changes to this gene may help explain why domesticated dogs are awake during the day rather than nocturnal like most wolves. Other Kidd's lab identified in dogs have overlap with human syndromes resulting from improper development of , including facial deformities and hypersociability. These parallels between and humans are what make understanding dog genetics valuable.

Kidd explains, "We are using these changes that were selected for by humans for thousands of years as a way to understand the natural function and gene regulatory environment of the neural crest in all vertebrates."

Explore further: Study shows domestication of dogs led to an increase in harmful genetic changes

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Porgie
1 / 5 (2) Jun 28, 2018
I know lets call it "evolution"! I know you want me to have the noble prize. But someone else thought of it and now her ewe have it again. Evolution of dogs, to gain food shelter, safety and mates. Wow who would have thunk it?
NormMackey
5 / 5 (1) Jun 30, 2018
The way Just So Stories creep into this particular subject is fascinating. Now, this change explains why wolves went from nocturnal to diurnal when becoming dogs. Unfortunately as researchers have noted, "Despite their Hollywood portrayal as nighttime prowlers, wolves tend to hunker down at night because their vision is not optimized for nocturnal hunting."

Missed. Explaining an invented, nonexistent difference between wolves and dogs. Or perhaps more perpetuating the disinformation.
rrwillsj
3 / 5 (2) Jul 01, 2018
The most noticeable difference between wolves & dogs are the differences in behavior. A feral wolf will not put up with being stared at. A cage-raised wolf, such as at a zoo, will barely tolerate being stared ar, Causes them a lot stress.

A dog expects to be stared at by it's human pack-mates. It may or may not tolerate being stared at by strangers. Depends on the dog's personality & how well socialized it is to people.

A big difference is that dogs will respond to human speech & posture. Can learn to respond to whistling, shouting & hand-signals from humans.

A neighbor's aussie sheepdog would leap the fence when she heard the nearby elementary school letting out. As the children bunched up at the street corner. Barking, the dog would herd them in a tight mass and then down the block before letting them go. Returning to herd the next group of kids.

Exasperated, my wife had me interfere. A few whistles & a hand-sweep would send the dog back to her yard.

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