Junctional Epidermolysis Bullosa 1 (JEB1)

Description

Junctional Epidermolysis Bullosa (JEB) is an inherited skin disease also known as Red Foot Disease or Hairless Foal Syndrome. Variations of the disorder affect Belgian Draft horses, American Saddlebred horses, and relatives of these breeds. This test detects the JEB1 variant found in Belgian Draft horses and related draft breeds.

JEB1 is caused by an insertion in the LAMC2 gene (c.1368insC), which shifts the reading frame and introduces a premature stop codon. LAMC2 encodes one of the three subunits of laminin-5, a protein essential to anchoring skin and mucosa to the underlying tissue, and the truncated protein is non-functional. The same variant has been identified in Belgian Draft horses and in the Breton and Comtois French draft breeds.

Affected foals are typically born alive with few signs. Four to five days after birth, skin lesions begin to develop at pressure points around the body and quickly spread into larger patches. Because laminin-5 is also involved in hoof attachment, the foal begins to lose the hoof, which may detach entirely. Foals may also develop oral ulcers and eroded enamel, and are typically born with incisor teeth, whereas normal foals do not develop teeth until around eight days of age.

There is no cure for JEB. As the condition worsens, foals develop severe infections and suffer increasing pain and discomfort. Affected foals die from these infections or are euthanized within 3 to 8 days after birth.

JEB is inherited as an autosomal recessive trait, so a foal must inherit two copies of the variant to be affected. Carriers have one copy and show no signs of disease. If two carriers are bred, each foal has a 25% chance of being affected and a 50% chance of being a carrier. Because affected foals do not survive to breeding age, every affected foal comes from a carrier-to-carrier mating. Carriers need not be removed from the breeding pool; a carrier bred to a clear horse will never produce an affected foal, so DNA testing allows breeders to keep valuable bloodlines while avoiding affected foals.

Animal Genetics offers DNA testing for both the JEB1 variant found in Belgian Draft horses and the JEB2 variant found in American Saddlebred horses.

Possible results

Breeds Affected

American Cream Draft Horse, Belgian Draft Horse, Brabant, Draft Horse, Draft Trotter, Percheron Cross, Spotted Draft Horse, Sugarbush Harlequin Draft

Reference

A mutation in the LAMC2 gene causes the Herlitz junctional epidermolysis bullosa (H-JEB) in two French draft horse breeds.

[PMID: 12633536]