Why pugs, bulldogs have flat faces decoded

Scientists have identified the genetic mutation that causes dogs such as pugs and bulldogs to have flat shaped faces, a finding that may help understand causes of birth defects that affect head development in human babies.
The research reveals new insights into the genes that underpin skull formation in people and animals.
Researchers at the University of Edinburgh in the UK analysed DNA samples from 374 pet dogs of various pedigree and mixed breeds.
All of the animals underwent body scans producing detailed 3D images of their heads.
These high-resolution CT scans enabled the researchers to take precise measurements of the shape of the dog's skull.

"Our results shed light on the molecular nature of this type of skull form that is so common and popular among dogs," said Jeffrey Schoenebeck, from the University of Edinburgh.

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.
Babies are sometimes born with brachycephaly too, though little is known about its causes.

Scientists said that screening children for changes in the SMOC2 gene could help to diagnose the condition.
The study was published in the journal Current Biology.