What Gene is Mutated in SCID?

Severe Combined Immunodeficiency (SCID), a recessive genetic defect of the immune system, affects Arabian and part-Arabian horses. The mutation responsible for SCID is a five-base pair deletion in the DNA-dependent protein kinase gene, resulting in a truncation of the protein.

The genetic defect leads to the lack of activity of the enzyme DNA-dependent protein kinase (DNA-PK), which is critical for the development of immune system diversity and its ability to protect against infections. As a result, SCID foals have increased susceptibility to infection by viral, bacterial, fungal, and protozoan organisms.

Matings between two carriers of the SCID mutation have a 25% chance of producing an affected foal. The carriers can transmit this severe combined immunodeficiency variant to 50% of their offspring. On the other hand, matings between a carrier and a non-carrier will result in offspring that are not affected by SCID but may still be carriers themselves.

The prevalence of the SCID mutation is estimated to be between 1-8% in Arabian horses, varying by country. Testing for this SCID variant can help breeders and owners identify carrier horses and select mating pairs accordingly to avoid producing affected foals.

SCID affects both male and female foals equally, and unfortunately, affected foals do not survive past the first six months of life. The signs of SCID typically appear between 2-8 weeks of age, including elevated temperature, respiratory stress, and diarrhea.

Early detection through testing is crucial to prevent the spread of this fatal condition in horse populations. By understanding the genetic basis of SCID and how it affects Arabian horses, breeders and owners can take proactive measures to protect these beautiful animals and ensure their survival for generations to come.

What gene is mutated in scid