With their squashed noses and wrinkled faces, they have become a favourite with dog lovers

Now, scientists believe they have uncovered a genetic mutation behind why some dogs - such as pugs and bulldogs - have flat faces.

The researchers hope it may also shed light on the causes of birth defects that affect babies' head development in the womb.

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CT scans  enabled the researchers to take precise measurements of the shape of the dog's skull.  By comparing the dogs' genetic information with measurements of their skulls, the team were able to pinpoint DNA variations that are associated with different head shapes

CT scans  enabled the researchers to take precise measurements of the shape of the dog's skull.  By comparing the dogs' genetic information with measurements of their skulls, the team were able to pinpoint DNA variations that are associated with different head shapes

THE HEALTH ISSUES 

The broad head shape seen in these dogs did not evolve naturally, and is instead the result of selective breeding.   

The facial structure of flat-faced dogs forces the breathing passages to be very compact. 

This, along with other structural elements of the body can lead to issues that include:

- Difficulty breathing when exercising

- Excess noises such as snorting and snoring

- Inability to properly regulate body temperature, which leads to heavy panting 

- An elongated palate, which can cause episodes of reverse sneezing which can consist of excessive gasps and wheezes 

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Vets are long warned against buying fashionable 'flat-faced' dogs amid concerns over their health and welfare.

The dogs, such as French bulldogs, pugs and Pekingese, are bred to emphasise certain 'cute' features which make them susceptible to a number of severe health problems, including difficulty breathing, infection and eye problems.

Researchers at the University of Edinburgh's Roslin Institute wanted to find out exactly what causes these flat features. 

They analysed DNA samples from 374 pet dogs of various pedigree and mixed breeds, that were being treated at the Royal (Dick) School of Veterinary Studies.

All of the animals underwent body scans as part of their care, producing detailed 3-dimensional images of the dogs' heads.

These high-resolution images - called CT scans - enabled the researchers to take precise measurements of the shape of the dog's skull.

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Share 141 shares With their squashed little noses and wrinkled faces, they have become a favourite with dog lovers. But owning and breeding designer dogs like pugs and bulldogs is 'self-indulgent', according to Lord Gardiner&nbsp;

With their squashed little noses and wrinkled faces, they have become a favourite with dog lovers Now, scientists believe they uncovered a genetic mutation behind why some dogs - such as pugs (pictured) and bulldogs - have flat faces

By comparing the dogs' genetic information with measurements of their skulls, the team were able to pinpoint DNA variations that are associated with different head shapes.

One variation - found to disrupt the activity of a gene called SMOC2 - was strongly linked to the length of the dog's face.

Animals with the mutation had significantly flatter faces, a condition called brachycephaly.

Lead researcher Dr Jeffrey Schoenebeck, of the University's Roslin Institute, said: 'Our results shed light on the molecular nature of this type of skull form that is so common and popular among dogs.'

Babies are sometimes born with brachycephaly, but until now scientists had no answers as to why.

Now they reckon screening children for changes in the SMOC2 gene could help to diagnose the condition. 

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