Junctional Epidermolysis Bullosa 1 (JEB1)
Gene or Region: LAMC2
Reference Variant: no change in LAMC2
Mutant Variant: insertion of C nucleotide
Affected Breeds: Belgian, Breton, Comtois
Research Confidence: High - Findings reproduced multiple studies
Explanation of Results: jeb1/jeb1 = homozygous for Junctional Epidermolysis Bullosa 1, trait expressed jeb1/n = heterozygous for Junctional Epidermolysis Bullosa 1, carrier n/n = no variant detected
Understanding JEB in Foals: Hairless Foal Syndrome Explained
Junctional Epidermolysis Bullosa 1 (JEB1), also known as red foot disease or hairless foal syndrome, results in the inability to produce the proteins needed to keep the skin on the body. Affected foals exhibit symptoms within days of birth, including blisters at the pressure points, detachment of the hooves, and oral ulcers. As there is no treatment, affected foals are humanely euthanized. JEB1 is an autosomal recessive condition, thus a horse must inherit two copies of the allele (jeb1/jeb1) to show any signs. Horses with only one copy of the variant (jeb1/n) are known as carriers due to their ability to produce affected foals.
Gene Information
LAMC2 is a subunit of a key component of basement membranes. Mutations in other subunits of this complex have been shown to result in JEB in many human populations. This particular mutation is a single base insertion that disrupts the normal amino acid sequence, resulting in an early stop codon and truncated protein.
References
Spirito F et al., “Animal models for skin blistering conditions: absence of laminin 5 causes hereditary junctional mechanobullous disease in the Belgian horse.” (2002) J Invest Dermatol. 119: 684-91. PMID: 12230513
Milenkovic D et al., “A mutation in the LAMC2 gene causes the Herlitz junctional epidermolysis bullosa (H-JEB) in two French draft horse breeds.” (2003) Genet Sel Evol. 35: 249-56. PMID: 12633536
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