Breathing Problems in Pugs and Bulldogs Might Have a Genetic Component

It might not be their smushed-up snouts after all

They're all good dogs. ( Frank Gaglione / Getty)

By Jason Daley

smithsonian.com 

Smushed-up faces are what make certain dog breeds, like French and English bulldogs or pugs, so
ugly-cute. But those good looks come with a cost. Many dogs in these breeds suffer from a disease
called Brachycephalic Obstructive Airway Syndrome (BOAS). The compact architecture of their
skull results in deformation, which make their nostrils or soft palate too small, obstructing airflow
and leaving the pups gasping for breath. Researchers long thought that the main cause was their
shortened faces. But genes found in another breed suggest that the shortness of breath might be in
their DNA, according to a new study published in the journal PLOS Genetics.

Ed Cara at Gizmodo reports that veterinarians began to notice that another small breed of dog, the
Norwich terrier, was increasingly coming down with similar respiratory symptoms, a disease called
upper airway obstructive syndrome. Unlike flat-faced pugs and bulldogs, however, the Norwich—
bred for chasing rodents—has a nice, proportional skull. That got study author Jeffrey Schoenebeck,
a veterinary scientist at the University of Edinburgh, wondering if the breathing problems in all the
small dogs were genetic.

“That made us wonder if there was something similar shared across these different breeds, or if we
were seeing two different diseases that just looked very similar,” he says.

Schoenebeck and his team decided to dig into the terrier’s DNA to find out. The team assessed 401
Norwich terriers for signs of the airway syndrome and also examined their genomes. Cassie Martin
at Science News reports the researchers discovered one gene mutation in particular, ADAMTS3,
was associated with the breathing disorder. Dogs with two copies of the mutation showed signs of
fluid retention and swelling around the lungs. They had worse breathing scores than dogs with just
one copy of the mutation or the normal gene.

When the team examined the genome of bulldogs and pugs, they also found that ADAMTS3 was
common, meaning their funky faces might not be the only cause of BOAS.

“BOAS is a complex disease. Although skull shape remains an important risk factor, our study
suggests that the status of ADAMTS3 should be considered as well,” Schoenebeck says in a
press release. “More studies are needed to dissect the complex nature of this devastating disease.”

Cara reports that Norwich terrier breeders are already inadvertently combating the mutation. In
Switzerland, Schoenebeck’s team has been working with breeders to give dogs breathing tests,
identifying pups likely to develop the disease. As a result, the younger generation of terriers is
less like to develop the disease than older dogs.

“In the 90s, something like 80 percent of the Norwich terriers that came into their clinic had poor
breathing and this mutation,” Schoenebeck tells Cara. “But it’s decreasing further and further over
time. They didn’t know it at the time, but they were actually selecting against this thing that we
think is causing this disease.”

The genetic finding means that researchers can now screen directly for the mutation, and perhaps
rid the terrier population of the disease.

The problem in flat-faced breeds may not be quite as simple to deal with. Wonky skull shape still
makes the risk of developing BOAS higher, and the gene mutation adds to that risk. The team needs
to do a similar study with bulldogs to figure out how much of their breathing problems come from
their genes and how much comes from their cute little smushed-up skulls.

Smushed-up faces are what make certain dog breeds, like French and English bulldogs and pugs,
so ugly-cute. But those good looks come with a cost. Many dogs in these breeds suffer from a disease
called Brachycephalic Obstructive Airway Syndrome (BOAS). The compact architecture of their
skull results in deformation, that make the nostrils or soft palate too small, obstructing airflow and
leaving the pups gasping for breath. Researcher long thought that the main cause was their shortened
faces. But genes found in another breed suggest that the shortness of breath might be in their DNA.

Ed Cara at Gizmodo reports that veterinarians began to notice that another small breed of dog, the
Norwich Terrier, was increasingly coming down with similar respiratory symptoms, a disease called
Upper Airway Syndrome. Unlike flat-faced pugs and bulldogs, however, the Norwich, bred for
chasing rodents, has a nice, proportional skull. That got Jeffrey Schoenebeck of the Roslin Institute
at the University of Edinburghand and lead author of the study in the journal PLOS Genetics
wondering if the breathing problems in all the small dogs were genetic.

“That made us wonder if there was something similar shared across these different breeds, or if we
were seeing two different diseases that just looked very similar,” he says.

Schoenebeck and his team decided to dig into the terrier’s DNA to find out. The team assessed 401
Norwich Terriers for signs of the airway syndrome and also examined their genomes. Cassie Martin
at Science News reports the researchers discovered one gene mutation in particular, ADAMTS3,
was associated with the breathing disorder. Dogs with two copies of the mutation showed signs of
fluid retention and swelling around the lungs. They had worse breathing scores than dogs with just
one copy of the mutation or the normal gene.

When the team examined the genome of bulldogs and pugs, they also found that ADAMTS3 was
common, meaning their funky faces might not be the only cause of BOAS.

“BOAS is a complex disease. Although skull shape remains an important risk factor, our study
suggests that the status of ADAMTS3 should be considered as well,” study leader Jeffrey Schoenebeck
says in a press release. “More studies are needed to dissect the complex nature of this devastating
disease.”

Cara reports that Norwich Terrier breeders are already inadvertently combating the mutation. In
Switzerland, Schoenebeck’s co-authors have been working with breeders to give dogs breathing tests,
identifying doggos likely to develop the disease. As a result, the younger generation of terriers is less
like to develop the disease than older dogs.

“In the 90s, something like 80 percent of the Norwich Terriers that came into their clinic had poor
breathing and this mutation,” Schoenebeck tells Cara. “But it’s decreasing further and further over
time. They didn’t know it at the time, but they were actually selecting against this thing that we think
is causing this disease.”

The genetic finding means that researchers can now screen directly for the mutation, and perhaps
rid the terrier population of the disease.

The problem in flat-faced breeds may not be quite as simple to deal with. Wonky skull shape still
makes the risk of developing BOAS higher, and the gene mutation adds to that risk. The team needs
to do a similar study with bulldogs to figure out how much of their breathing problems come from
their genes and how much comes from their cute little smushed-up skulls.


Read more: https://www.smithsonianmag.com/smart-news/breathing-problems-smushy-
faced-dogs-might-have-genetic-component-180972215/#wPluhHi8rlcfsV6S.99
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