Researchers are discovering new traits of a genetic defect that affects muzzle length and caudal vertebrae in dogs
A recent genetic study at the University of Helsinki provides new information on the incidence of a DVL2 genetic defect associated with the nail tail and its importance for canine constitution and health. The variant has been found in several Bulldog and Pit Bull subspecies, and has been shown to lead to caudal spine deformities and muzzle shortening. The DLV2 variant may also affect cardiac development.
The dog breed often focuses on appearance. In some breeds, the ideal body shape is bulky, with a broad head and short muzzle, short legs and a very short, curvy tail, also known as the “spiral tail”. In a previous study conducted in the United States, the screw tail was linked to a variant in the DVL2 gene. The variant has been enriched in English Bulldogs, French Bulldogs and Boston Terriers due to inbreeding. In addition to the shape of the tail, the DVL2 variant has been proposed to contribute other features typical of the aforementioned breeds, in addition to what is known as Rubino-like syndrome. However, its specific effects on body shape and health remained unclear at the time.
“In this study, we wanted to further investigate the frequency of the DVL2 variant in different dog breeds and determine its effects on skeletal growth. The variant was identified in several Bulldog and Pit Bull subspecies, some of which had both the normal form and the genetic variant. This made it possible to investigate The consequences of the variable, “says Julia Niskanen, PhD researcher from the University of Helsinki and the Research Center Folkholsan.
The prevalence of the DVL2 variant varied widely between strains. All English bulldogs, French bulldogs, and Boston Terriers in the study were homozygous for the variant, that is, they inherited the variant from both parents. In other words, the normal form of the gene was not found in these strains. Both variant and regular form are found in American Staffordhire Terriers, Staffordshire Bull Terriers, Dogues de Bordeaux, Olde English Bulldogges, and American Bulldogs.
To determine the effect of the variant on body shape, the researchers analyzed the skeletal anatomy of the American Staffordshire Bull Terriers for different genotypes through a CT scan that was performed in the Veterinary Teaching Hospital. The results clearly showed that the DVL2 gene defect produces abnormalities in the caudal vertebrae in the homozygous state.
“However, tail deformities in American Staffordhire Terriers were less severe than helix tails commonly seen in English Bulldogs, French Bulldogs, and Boston Terrier. Contrary to the previous study, we did not find an association between the DVL2 variant and thoracic vertebral malformations,” says the vet and teacher Clinical clinical director Philma Rionanin from the University of Helsinki College of Veterinary Medicine.
Another major finding in the study is that the genetic defect affects muzzle length to varying degrees in homozygous dogs, the muzzle is much shorter than heterozygous dogs, which carry only one copy of the gene defect. Likewise, heterozygous dogs have shorter muzzles than dogs that do not have any copies of the gene defect.
“In addition to the effects on the skeletal system, we discovered that many DVL2 homozygous dogs have a congenital heart defect. However, this is a preliminary finding that requires further study. If confirmed, it could partially explain the prevalence of congenital heart defects in the breeds. Certain, “adds PhD researcher Niskanen.
In addition to the DVL2 gene defect, many strains also have other genetic variants that affect body shape. Their combined effects may lead to serious health problems. For example, a short muzzle predisposes dogs to humeral obstructive airway syndrome (BOAS), whose symptoms include breathing difficulties and a lack of tolerance to exercise. The prevalence of the genetic defect demonstrates that, in some strains, the health problems associated with DVL2 can be prevented with gene testing. In some breeds, Docent Marjo Hytönen of the University of Helsinki and the Folkhälsan Research Center explains that there is no longer any difference, making it impossible to improve the situation with current breeding programs.