Intestinal cobalamin malabsorption / IGS (CUBN-related) - Border Collie

What does this test assess?

This genetic test analyses the CUBN c.8392delC variant in the Border Collie. The condition is known as Imerslund-Gräsbeck syndrome, IGS, selective intestinal cobalamin malabsorption, intestinal cobalamin malabsorption, ICM, inherited vitamin B12 malabsorption and CUBN-related cubilin deficiency. CUBN encodes cubilin, part of the cubam complex required for uptake of vitamin B12, also called cobalamin, from the intestine.

What does this condition mean?

Vitamin B12 is needed for normal blood formation, growth, energy metabolism and nerve function. In IGS/ICM, the dog cannot absorb enough dietary vitamin B12 through the intestine. Natural stores become depleted in young puppies, leading to a combination of digestive, blood and metabolic problems.

In Border Collies, the first signs can appear during the first weeks to months of life. Possible signs include poor appetite, poor weight gain, swallowing difficulty, painful tongue ulcers, chronic diarrhoea, irregular heart rhythm, anaemia and chronic fatigue. Because puppies with vitamin B12 deficiency can deteriorate quickly, a clear genetic result is highly practical.

Inheritance and result

The trait is inherited as an autosomal recessive condition. Dogs with two copies of the tested CUBN variant develop IGS/ICM for this variant. Carriers have one copy, are usually healthy themselves, but can pass the variant to offspring.

• Clear: the tested variant was not detected.
• Carrier: one copy of the variant was detected; important for breeding plans.
• Affected: two copies were detected; this genotype causes CUBN-related IGS/ICM for this variant.

Practical value of this test

This test gives breeders and owners clear information before a mating is planned or when young dogs show signs compatible with vitamin B12 malabsorption. Because carriers can look normal, DNA testing is the most direct way to identify risk matings.

• Helps identify carriers before breeding.
• Reduces the risk of affected puppies from carrier x carrier matings.
• Provides targeted genetic context in young dogs with poor growth, lethargy or blood abnormalities.
• Supports transparent communication with buyers, veterinarians and breed clubs.