Screw Tail (ST Locus, Bulldog and Terrier Type)
Affected Genes: DVL2
Inheritance: Autosomal Incomplete Dominant with Incomplete Penetrance and Variable Expressivity
Variant(canFam6):
chr5:32333348: 1 bp deletion G
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.
References:
Mansour TA, Lucot K, Konopelski SE, Dickinson PJ, Sturges BK, Vernau KL, Choi S, Stern JA, Thomasy SM, Döring S, Verstraete FJM, Johnson EG, York D, Rebhun RB, Ho HH, Brown CT, Bannasch DL. Whole genome variant association across 100 dogs identifies a frame shift mutation in DISHEVELLED 2 which contributes to Robinow-like syndrome in Bulldogs and related screw tail dog breeds. PLoS Genet. 2018 14(12):e1007850.
Niskanen JE, Reunanen V, Salonen M, Bannasch D, Lappalainen AK, Lohi H, Hytönen MK. Canine DVL2 variant contributes to brachycephalic phenotype and caudal vertebral anomalies. Hum Genet. 2021 140(11):1535-1545.