Quick Summary
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Phenotype: Junctional epidermolysis bullosa (JEB) is an inherited disease that causes moderate to severe blistering of the skin and mouth epithelia, and sloughing of hooves in newborn foals, and progresses to skin lesions with age. Two causal variants have been identified: one, called J, explains this disease in Belgians and related draft breeds; and another, called J2, is found in Saddlebreds and related breeds. It is likely that additional yet-unidentified variants may exist that explain the JEB phenotype in other breeds.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, J =Junctional epidermolysis bullosa, Belgian variant
Breeds appropriate for testing: Belgian, Breton, Comtois
Explanation of Results:
- Horses with N/N genotype will not have junctional epidermolysis bullosa and will not transmit this JEB variant to their offspring.
- Horses with N/J genotype will not have junctional epidermolysis bullosa, but are carriers. They may transmit this JEB variant to 50% of their offspring. Matings between two carriers result in a 25% chance of producing a JEB-affected foal.
- Horses with J/J genotype will have junctional epidermolysis bullosa, a fatal condition.
$45 one test per animal
*Members of the Belgian Draft Horse Corporation of America are advised to order testing directly through the registry.*
Sample Collection
Horse DNA tests are carried out using cells from the roots of a hair sample (roughly 20-30 hairs).
1. Grab about 10 hairs at the base.
2. Wrap the hairs around your finger and give it a quick pull.
3. Check the ends to make sure the pulled hairs have roots.
4. Repeat the process until you have collected about 20-30 hairs with intact roots.
5. You can choose different places on the mane or tail. NOTE: For foals, we recommend pulling all hairs from the tail only.
6. Tape the hairs to the submission form and fold the form along the dotted line to protect the sample. Do not use ziploc bags as they can cause condensation that allows mold to grow on the hair.
7. Place the folded form containing the sample in a paper envelope and mail it to the laboratory.
Junctional epidermolysis bullosa (JEB) is an inherited disease that causes moderate to severe blistering of the skin and mouth epithelia, and sloughing of hooves in newborn foals. This condition is also known as red foot disease, and was previously known as epitheliogenesis imperfecta (EI) in American Saddlebred horses. Affected foals are typically born alive, but soon develop skin lesions at pressure points. The condition worsens with time and the foal eventually succumbs to severe infection or has to be euthanized.
Junctional epidermolysis bullosa across species has been associated with mutations in three genes (LAMA3, LAMB3, LAMC2) that each encode the three subunits of laminin-5, a glycoprotein vital to the integrity of the skin and mucosa. In horses, mutations in LAMA3 and LAMC2 have been shown to result in JEB.
In Belgian Draft horses and derivatives of that breed, a recessive mutation J in the LAMC2 gene (AY082802.1:c.1571_1572insC) was identified as the cause of junctional epidermolysis bullosa. The insertion in LAMC2 results in a premature termination codon and thus a non-functional laminin-5.
Two copies J are required to develop junctional epidermolysis bullosa. Since affected animals do not survive to breeding age, JEB foals are produced by matings between carrier animals. The VGL offers diagnostic DNA tests that detects the known causal variants for JEB. Breeders can reliably use test results to enhance breeding strategies to avoid producing affected foals. Carriers do not need to be removed from the breeding pool. A successful breeding program can use matings of carriers (N/J) to non-carriers (N/N) without the worry of producing an affected foal.