Screw Tail (ST Locus, Bulldog and Terrier Type)

General Information: ST Locus (ST) (screw tail) is a type of natural short tail of the caused by malformations and fusions of the vertebrae, resulting in a kinked appearance. This trait is characteristic of breeds such as Bulldogs, French Bulldogs, and Boston Terriers but can also appear in other breeds. The gene responsible, DVL2, not only affects tail shape but also contributes to the brachycephalic skull type, leading to very short noses. Dogs with two copies of the DVL2 gene mutation can experience a range of spinal vertebral abnormalities, including hemivertebrae, making this trait more than just an appearance issue. Symptoms may include a shortened, kinked tail, and associated health problems such as brachycephalic airway obstruction syndrome, malformed thoracic vertebrae, and congenital heart disease. Due to the variability in how this gene is expressed, genetic testing is often required to determine the presence of the gene.

Gene / Testing Information: Genetic testing for the ST Locus (ST) (Screw Tail) involves screening for the DVL2 gene mutation, which causes the distinctive kinked or screw tail phenotype. This trait is inherited in a recessive manner, meaning a dog must inherit two copies of the mutated gene (one from each parent) to develop the characteristic screw tail. Dogs with one copy of the mutation (N/P) are carriers and do not show clinical signs but can pass the gene to their offspring. Breeding two carriers (N/P) has a 25% chance of producing an affected puppy (P/P) and a 50% chance of producing another carrier. To avoid health issues and maintain breed standards, it is recommended to perform genetic testing before breeding. Breeding two affected dogs (P/P) should be avoided due to the associated health risks. Genetic testing ensures responsible breeding practices and helps eliminate the mutation from breeding lines, reducing the risk of producing affected pups.