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Glycogen Branching Enzyme Deficiency (GBED)
| Acronym: | GBED |
| Gene: | GBE1 |
| Mutation: | c.102C>A |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Glycogen branching enzyme deficiency (GBED) is a metabolic disease that results in late abortions or stillbirths. GBED is found in Quarter horses and its related breeds. GBED is caused by a genetic mutation in the GBE1 gene which encodes the glycogen branching enzyme. The mutation results in improper glycogen storage and makes tissues unable to maintain glucose homeostasis. Foals that survive at birth usually live up to a few weeks experiencing weakness, limb deformities, seizures followed by cardiac and respiratory failure. However, the majority of affected offspring will be stillbirths because of the importance of glycogen during embryonic development.
GBED is inherited as an autosomal recessive trait. This means that two copies of the mutated gene are required for the disease to develop. Horses that have only one copy of the mutated gene remain healthy but act as carriers that can potentially pass the mutation to their offspring. The disease is incurable, but early detection by genetic testing can help identify disease carriers and prevent further breeding by proper selection of mating pairs.
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:
Brosnahan MM, Brooks SA, Antczak DF. Equine clinical genomics: A clinician’s primer. Equine Vet J. 2010;42(7):658-670. doi:10.1111/j.2042-3306.2010.00166.x