dog babyStudies of dog DNA have led to the discovery of a genetic mutation linked to flat face shapes which could eventually support the diagnosis of abnormal skull condition in children.The researchers are stationed at the University of Edinburgh’s Roslin Institute, the birthplace of Dolly the cloned sheep, explains The National.

The DNA samples from 374 pet dogs of various pedigree and mixed breeds which were being treated at the Royal School of Veterinary Studies were analysed. Each animal later underwent a CAT scan, producing detailed 3D images of their heads. This allowed the scientists to take precise measurements of the shape of the dog’s skull and then identify DNA variations associated with different head shapes.

Through comparing the dogs’ genetic information with their skull measurements, the team were able to locate the genetic variations associated with different head shapes.  One particular variation, which was found to disrupt the activity of a gene called SMOC2 – was strongly linked to the length of the dog’s face. Animals with this mutation, such as pugs and bulldogs, had significantly flatter faces, a condition called brachycephaly.

Dr Jeffrey Schoenebeck, lead researcher, commented, “Our results shed light on the molecular nature of this type of skull form that is so common and popular among dogs.”

He and his team had planned to discover the genes involved in human craniofacial anomalies, specifically craniosynostosis. This is a rare skull problem that causes a baby to be born with, or develop, an abnormally shaped head. This irregular skull shape can cause persistent headaches, learning difficulties, eye problems and other symptoms, most of which develop in later childhood. The symptoms usually result from increased pressure within the skull, known as intracranial pressure (ICP).

Another anomaly is midface hypoplasia, in which the upper jaw, cheekbones and eye sockets have not grown as much as the rest of the face. As a result of this, the child’s eyes can seem large, appearing “bug-eyed”, and their upper teeth usually do not meet the lower teeth well.

This causes an “under bite” appearance which makes the lower jaw appear as if it’s sticking out more than usual. This can in fact, be so severe that people develop snoring and sleep apnea where sleep is disturbed because they are waking up due to lack of air.

In their study, published in the journal Current Biology, the team describe the mammalian skull as an “architectural wonder”. They explained, “The skull facilitates ingestion and respiration, provides protection for the brain, and houses the visual, auditory, and olfactory systems. The skull also functions in communication, defence, and reproductive behaviours.”

In human and canine species, they said brachycephaly and midfact hypoplasia were risk factors for developing severe morbidities, including respiratory, those related to the ears and eyes and neurological abnormalities.

The study concluded, “Our results suggest that SMOC2 should be screened as a candidate for diagnosis. Not to be ignored, the role of the SMOC2 dysfunction and the associated haplotype we defined need further exploration as they concern the health of brachycephalic dogs.

“As our canine skull project continues to grow, we will explore the role of SMOC2 and other skeletal QTL with comparative health implications.”