Bulldog screw tails linked to human genetic disease

Bulldogs and their French counterparts are among the most popular of dog breeds around the world. Now researchers from the University of California, Davis, School of Veterinary Medicine have found the genetic basis for these dogs' appearance, and linked it to a rare inherited syndrome in humans.

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he study has been published in the journal PLOS Genetics.

Bulldogs along with Boston terriers have a feature not found in other breeds, a short, kinked tail or 'screwtail' according to Professor Danika Bannasch, Department of Population Health and Reproduction in the UC Davis School of Veterinary Medicine. According to researchers, these three breeds lack the vertebrae that make up the tail bone.

Researchers sequenced the entire DNA sequence of 100 dogs, including 10 from screwtail breeds and from 12 million individual differences they were able to indentify one mutation, in a gene called DISHEVELLED 2 or DVL2. The variant was found in 100 per cent of the bulldogs and French bulldogs as well as Boston terriers.

According to Professor Henry Ho at the UC Davis School of Medicine who studies similar genes in humans, mutation in the related DVL1 and DVL3 genes are known to cause Robinow syndrome, a rare inherited disorder in humans characterised by strikingly similar anatomical changes. These include a short, wide "babyface," short limbs and spinal deformities. In addition to these, Robinow patients and the screwtail breeds also share another disease trait, the cleft palate.

Notably, in both humans and dogs, DVL genes are part of a signalling pathway called WNT that is involved in development of the skeleton and nervous system, among other things, said Peter Dickinson, professor of surgical and radiological sciences at the School of Veterinary Medicine.

By characterising the screwtail DVL2 protein product, Sara Konopelski, a graduate student the Ho lab, pinpointed a key biochemical step in the WNT pathway that is disrupted by the mutation. This finding further suggests that a common molecular defect is responsible for the distinct appearances of both Robinow patients and screwtail dog breeds.

According to Dickinson, the mutation is so common in the dogs that it would be difficult to remove it by breeding.