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Severe Combined Immunodeficiency (PRKDC gene, Jack Russell Terrier)

Severe Combined Immunodeficiency (PRKDC gene, Jack Russell Terrier)

Severe combined immunodeficiency (SCID) is a rare genetic disease characterized by a dysfunctional or absent immune system.

Symptoms

The immune system of a dog with SCID cannot produce T and B lymphocytes, the immune cells that fight infection and disease. This means that affected puppies are highly susceptible to infections, even those that would not normally be problematic for a dog with a healthy immune system. This affects the puppies' survival and hinders their proper development and growth.

Disease Management

There is currently no cure for SCID and no specific treatments are available. Puppies usually do not survive beyond 4 months.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Severe combined immunodeficiency (SCID) is a consequence of impaired B and T lymphocyte development that can be explained by defective V(D)J recombination, essential for the formation of unique antigens on lymphocytes, which is essential for the immune system to respond correctly to infections. As in humans, this disease in dogs causes affected animals to have serious immunity problems. The variant we studied is c.10849G>T of the PRKDC gene which produces an enzyme involved in the repair of DNA double-strand breaks and also plays a crucial role in the V(D)J recombination process. This variant was first identified in Jack Russell Terrier dogs by Ding et al. and was found to cause a premature stop codon and thus a PRKDC enzyme that has lost its function.

Most affected breeds

Jack Russell Terrier

Bibliography

Ding Q, Bramble L, Yuzbasiyan-Gurkan V,et al. DNA-PKcs mutations in dogs and horses: allele frequency and association with neoplasia. Gene. 2002 Jan 23;283(1-2):263-9.