Dog genetic studies reveal why Shar-Peis are wrinkled

Jan 13, 2010 by Lin Edwards report
Shar Pei puppies. Image: Natascha Seitler von Lucky

(PhysOrg.com) -- There are over 400 genetically different dog breeds, with massive variations in size, colors, fur type, temperament, and so on, and scientists have wondered exactly what changes in the genes have been brought about by centuries of selective breeding to explain the huge differences. Now a new study has shed some light on the puzzle.

The research, by Joshua Akey and colleagues from the University of Washington in Seattle in the US, sequenced large portions of the genes of 300 dogs of 10 pedigree breeds, including the Shar-Pei, Standard Poodle and Jack Russell. Their aim was to determine which areas were likely to have been involved in selective breeding and to identify the genes corresponding to selected physical features.

Unlike previous research, which began with the traits and looked for corresponding genes, Akey and his colleagues started with the genes and looked for regions that were different in the various breeds, and then looked for physical attributes that might be related to the changes. They located 155 distinct genetic regions that appeared to have been tampered with through breeding, including five genes that have been linked previously to differences between breeds.

The researchers found many genes that could have an influence on the size of the dog or the color of the coat, and they also identified specific differences in a gene that results in the wrinkled skin of the Shar-Pei. They made this identification by comparing the genes in 32 Shar-Peis with highly wrinkled skin to those of 18 Shar-Peis with smoother skin. Akey said he had decided to study the Shar-Pei particularly because there are rare in humans that also produce severe wrinkling.

The affected gene, HAS2 makes an enzyme (hyaluronic acid synthase 2) that is important in the production of . Akey speculated that a mutation occurred and a breeder liked the look of the wrinkled puppy and selectively bred for the trait.

Dogs have been domesticated for at least 10,000 years, but most of the breeds we know today have appeared only in the last few centuries. While in the early years no one knew about genetics, selective breeding has always involved selecting genes and influencing their expression.

The huge variations in dog breeds makes it easier to identify which genes produce particular phenotypes (physical traits), than it would be in a study of humans. Studying the changes in genes in dogs that result in the different body shapes, sizes and temperaments might also reveal genetic changes that could have produced breed-specific diseases and different behaviors.

Finding out what the genes in the dog do and how they have been changed by artificial selection for desired traits could also help scientists understand more about our own and their evolution by natural selection. Akey said this was the real reason people were interested in studying the genetics of dogs, although he said dogs were also fun to study.

The findings were published in the journal Proceedings of the National Academy of Sciences (PNAS) on January 11.

Explore further: Canola genome sequence reveals evolutionary 'love triangle'

More information: Tracking footprints of artificial selection in the dog genome, PNAS, DOI:10.1073/pnas.0909918107

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User comments : 24

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marjon
1 / 5 (2) Jan 13, 2010
Has any dog breed mutated into a new species yet?
Parsec
5 / 5 (1) Jan 13, 2010
Wolves and domestic dogs are separate species. So, yes of course they have.
Thrasymachus
5 / 5 (1) Jan 13, 2010
Depends on your definition of species. If you were an archeologist millions of years in the future, and confronted with a fossilized chihuahua and a fossilized mastiff, would you classify them as the same species? Even using the classical definition of a species, individuals that can naturally reproduce viable offspring together, chihuahuas and mastiffs are no longer the same species since they now need human help to produce crossbreeds.
marjon
1 / 5 (3) Jan 13, 2010
Wolves and domestic dogs are separate species. So, yes of course they have.

Why haven't dog breeds become separate species?

BTW, does anyone else think that creating new dog breeds is animal abuse?

JayK
3 / 5 (2) Jan 13, 2010
Marjon, until you have even an education that allows you to understand the science behind classic cladistry, please don't continue to make a fool of yourself. The multiple definitions of the word "species" is important, and you just ignored the fact that it was pointed out to you.
acarrilho
5 / 5 (1) Jan 13, 2010
Wolves and domestic dogs are separate species. So, yes of course they have.

Why haven't dog breeds become separate species?


If by "dog" you mean Canis Lupus Familiaris, because there hasn't been enough selective pressure... which is obvious to anyone with enough education on the matter to even warrant asking a question about it. If by "dog" you mean Canis Lupus... you figure it out.

BTW, does anyone else think that creating new dog breeds is animal abuse?


I bet every question for you has just a "yes" or "no" answer...
marjon
1 / 5 (2) Jan 13, 2010
Marjon, until you have even an education that allows you to understand the science behind classic cladistry, please don't continue to make a fool of yourself. The multiple definitions of the word "species" is important, and you just ignored the fact that it was pointed out to you.

'Species' has more than one scientific definition? How can biology progress with multiple definitions of the same word?
In real science like physics, terms must be specifically defined.

because there hasn't been enough selective pressure...

How much is 'enough selective pressure' to create a new species?
Thrasymachus
5 / 5 (1) Jan 13, 2010
What defines a species depends on the kinds of organisms being observed. Many Eukaryotes and most Prokaryotes do not reproduce sexually. Many plants have vastly different phenotypes and genotypes depending on the stage of their life cycle, and often self-fertilize. Some organisms display exceedingly similar phenotypes with vastly different genotypes, and vice-versa and neither reproduce sexually. Many different micro-organisms of differing species have been caught swapping genes. All of these phenomena contribute to a great deal of difficulty in formulating a general defining principle of a term like 'species.'

At the end of the day, 'species' is a formerly scientific term for a scheme of classification that now has very little function in the actual observations, theories and experiments of biology without significant additional definition and qualification. And wtf are you doing implying biology isn't a real science? In many ways, it's more real than theoretical physics.
marjon
1 / 5 (1) Jan 13, 2010
'species' is a formerly scientific term for a scheme of classification that now has very little function in the actual observations, theories and experiments of biology without significant additional definition and qualification.

Then why not stop using the term if it is so imprecise and unscientific?
ShotmanMaslo
3 / 5 (2) Jan 14, 2010
"Then why not stop using the term if it is so imprecise and unscientific?"

Because it is still useful, to describe reproductive behavior.
You could say that different species are groups of animals with reproductive barrier, but then you would have problems with ring species, horizontal gene transfer etc.

Species is a man-made definition. Nature does not care about our exact definitions. Life is more of a blended genetic cocktail than separate categories.

"Has any dog breed mutated into a new species yet?"

Not enough variation in their reproductive mechanism yet. Dog breeds are like human races on steroids.

"BTW, does anyone else think that creating new dog breeds is animal abuse?"

No, why? I dont think they suffer in any way...
Sinister181
3 / 5 (2) Jan 14, 2010
"No, why? I dont think they suffer in any way..."

Actually, they do. There are certain health problems associated with different breeds.

http://www.scampe...ds.shtml
marjon
2.3 / 5 (3) Jan 14, 2010
"BTW, does anyone else think that creating new dog breeds is animal abuse?"

No, why? I dont think they suffer in any way...


If a breed of dog is not found in nature, maybe there was a reason.
JayK
1 / 5 (2) Jan 14, 2010
Selective breeding has reduced world hunger and strife with corn, wheat, rice, cows, sheep, goats, fish and hundreds of other items. Selective breeding of dogs was done originally to breed for qualities that made human lives better. But thanks to marjon, I've seen the errors in the human way, and I will go on to tell the world that they should not tamper with the natural ways of nature!

And then I'll shut up and eat my Wheaties.

But before I go, please, marjon, can you extrapolate on your possible "reason"?
marjon
1 / 5 (1) Jan 14, 2010
People treat their pet dogs like children. Many breeds have specific, well documented medical problems such as hip dysplasia.
Why would anyone who claims to love animals want to buy a pet that has been proven to suffer painful genetic disorders so they can carry their dog in their purse?
We used to breed Holstein heifers with red Angus bulls because they produced calves with small heads allowing an easier birth. Hybrid animals and plants for agriculture are created to produce a more healthy and higher producing life form.
Sinister181
not rated yet Jan 14, 2010
"Selective breeding has reduced world hunger and strife with corn, wheat, rice, cows, sheep, goats, fish and hundreds of other items. Selective breeding of dogs was done originally to breed for qualities that made human lives better."

So basically, breeding a dog with unnecessary, non-beneficial features like a squashed nose and breathing difficulties is making human lives better. I see your argument. No, really, I do.
JayK
3 / 5 (2) Jan 14, 2010
Sinister181: Did you miss the key words "was done"? I said nothing of the ethics of current dog breeding. If you want to play that game, I'm sure PETA will take your donations. You can argue all day long whether designer dogs are ethical, but it has nothing to do with the science of canine reproduction. In the end, though, you'll be running into capitalists that just give people what they want, regardless of the ethics or anything else.
ShotmanMaslo
not rated yet Jan 14, 2010
I agree with marjon that selective breeding, if not done properly, could be considered animal abuse.
JayK
1 / 5 (1) Jan 14, 2010
So what does your outrage have to do with the science?
marjon
not rated yet Jan 15, 2010
So what does your outrage have to do with the science?

Science has no responsibility to be ethical?
JayK
1 / 5 (1) Jan 15, 2010
So what does your outrage have to do with the science?

Science has no responsibility to be ethical?


No one said that. Outrage != ethics. Outrage is emotional. Ethics define clear boundaries. Scientists didn't create 400 different dog breeds.
marjon
not rated yet Jan 15, 2010
So what does your outrage have to do with the science?

Science has no responsibility to be ethical?


No one said that. Outrage != ethics. Outrage is emotional. Ethics define clear boundaries. Scientists didn't create 400 different dog breeds.

How are such boundaries determined, with logic, emotion or both?
JayK
1 / 5 (1) Jan 15, 2010
There are plenty of cognitive science books that discuss the matter, why don't you run along and read a couple of them and get back to us with a nice book report on your findings?
marjon
1 / 5 (1) Jan 15, 2010
There are plenty of cognitive science books that discuss the matter, why don't you run along and read a couple of them and get back to us with a nice book report on your findings?

Then you agree emotion must be involved with ethics.
JayK
1 / 5 (1) Jan 15, 2010
My opinion is that emotion is too tied up in ethics for them to be truly effective and binding. However, without emotions (such as compassion and empathy) you can wind up with things that appear to society to be beyond the limits of acceptable study. There is a careful balance required between the human characteristics of compassion (emotion) and cold hard logic and that balance should be reviewed and tweaked. The problem is that there is no single person or group or committee that can be trusted to do that, so pure ethical values are a goal, but probably never a reality.