Border Collie Genetic Tests
Imerslund-Gräsbeck syndrome (IGS) is a disorder found in Beagles and Border Collies where dietary cobalamin (vitamin B12) is unable to be absorbed through the gut. Both breeds have independent mutations in the cubulin (CUBN) gene. The disease has an autosomal recessive mode of inheritance with both sexes being equally affected. Owners of IGS affected dogs often note a lack of appetite, failure to gain weight, lethargy and malaise that intensifies after eating. Clinically, anemia and excess urine protein is observed. Without chronic treatment, permanent brain and nervous system damage can occur. Dogs with one normal and one mutated IGS gene, carriers, are unaffected but breeding two carriers together would be predicted to produce 25% affected offspring and 50% carriers.
The VGL offers a test for inherited IGS in Beagles and Border Collies to assist owners and breeders in identifying affected and carrier dogs. The test uses DNA collected from buccal (cheek) swabs, thus avoiding blood sample collection. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.
Results reported as:
|N/N||No copies of the IGS mutation; dog is normal|
|N/IGS||1 copy of the IGS mutation; dog is a carrier|
|IGS/IGS||2 copies of the IGS mutation; dog is affected|
Fyfe JC, Hemker SL, Venta PJ, Fitzgerald CA, Outerbridge CA, Myers SL, Giger U. (2013) An exon 53 frameshift mutation in CUBN abrogates cubam function and causes Imerslund-Gräsbeck syndrome in dogs. Mol Genet Metab. 109(4):390-396.
Drögemüller M, Jagannathan V, Howard J, Bruggmann R, Drögemüller C, Ruetten M, Leeb T, Kook PH. (2013) A frameshift mutation in the cubilin gene (CUBN) in Beagles with Imerslund-Gräsbeck syndrome (selective cobalamin malabsorption). Anim Genet. Oct 27, DOI:10.1111/age.12094.
An inherited neutropenia (decrease in white blood cells) has been identified in Border Collies. This disease, called Trapped Neutrophil Syndrome (TNS), has been found to be caused by a mutation in the Vesicle Protein Sorting 13B (VPS13B) gene. Affected puppies suffer from chronic infections resulting from a compromised immune system, are often smaller than their littermates and have developmental delays. Additionally, a narrow elongated skull and slender extremities have been observed in some affected dogs. Affected individuals can have infections from as early as 6 weeks of age, while a few may have mild clinical signs that are not observed until age 2 or older. TNS is inherited as an autosomal recessive disease- thus both sexes are equally affected and 2 copies of the defective allele are required to produce the disease. The defective allele has been observed at a rate of 7-8% worldwide in Border Collies.
Test Results reported as:
N/N: No copies of TNS mutation, dog is normal.
N/TNS: 1 copy of TNS mutation; dog is normal but is a carrier. Breedings between carriers are expected to produce 25% affected offspring.
TNS/TNS: 2 copies of TNS mutation; dog is affected.
If a carrier is bred to a clear dog (N/N), 50% of the offspring will be carriers but no affected offspring will be produced. Breedings between carriers would be expected to produce 25% affected offspring.
This test is specific for the deletion in the VPS13B gene associated with TNS in Border Collies.
Reference: Shearman J.R. and A.N. Wilton. A canine model of Cohen syndrome: Trapped Neutrophil Syndrome. BMC Genomics 2011 12:258.