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Junctional Epidermolysis Bullosa 2 (JEB2)
| Acronym: | JEB2 |
| Gene: | LAMA3 |
| Mutation: | 6589-bp deletion |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Junctional epidermolysis bullosa 2 (JEB2) is an inherited skin disease that affects several breeds of horses. Horses with JEB2 have severe blistering of the skin and mouth epithelia and sloughing of hooves in newborn foals. Affected horses are born alive, but soon develop skin lesions at pressure points that worsen soon, and the horse succumbs to infection or has to be euthanized. JEB2 is caused by a genetic mutation in the laminin, alpha 3 (LAMA3) gene responsible for the organization of the epidermis, or the basement membrane that underlies the top layer of the skin. The deletion mutation in the LAMA3 gene impacts the strength of the skin and causes detachment of the epidermis from other layers of the skin.
JEB2 is inherited as an autosomal recessive disease meaning that two copies of the mutation are needed for a horse to be affected. JEB2 affects several horse breeds, such as Belgian, Breton, Comtois, and American Saddlebred horses. The disease is incurable, but early detection by genetic testing can enhance breeding strategies to identify carriers of the mutation and avoid producing affected horses.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Graves, K. T., Henney, P. J., & Ennis, R. B. (2009). Partial deletion of theLAMA3gene is responsible for hereditary junctional epidermolysis bullosa in the American Saddlebred Horse. Animal Genetics, 40(1), 35–41. doi:10.1111/j.1365-2052.2008.01795.x
Milenkovic, D., Milenkovic, D., Mata, X., Chadi, S., & Guérin, G. (2005). cDNA sequence of the horse (Equus caballus)LAMA3gene and characterization of two intronic SNP markers. DNA Sequence, 16(6), 468–473. doi:10.1080/10425170500287674