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Cerebellar Abiotrophy (CA)
| Acronym: | CA |
| Gene: | TOE1 |
| Mutation: | c.541-13539C>T |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Cerebellar abiotrophy (CA) is a genetic disease that affects mostly Arabian horses and their breeds. Cases of CA have also been reported in the Oldenburg, Eriskay, and Gottland pony. CA is a disease of progressive death of Purkinje neurons in the cerebellum causing horses to have tremors, lack of balance, startle, and fall easily. Also, symptoms of ataxia vary in horses with CA, some horses can experience exaggerated forelimb movement, dysmetria in thoracic limbs, or difficulty standing up from a lying position. Symptoms usually start to appear between 6 weeks and 6 months of age. The mutation responsible for this disease is in the target of the EGR1 (TOE1) gene involved in cell cycle regulation.
This type of cerebellar abiotrophy is inherited as an autosomal recessive trait, meaning both mutated TOE1 genes are required for the disease to develop. Horses heterozygous for the mutation, carrying one mutated and one normal gene, appear normal, without signs of the disease. Affected horses can usually be only pets since their coordination is not good enough to be ridden. Early detection by genetic testing can identify horses that are affected or carry the specific mutation, which is critical for the 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:
Brault, L. S., Cooper, C. A., Famula, T. R., Murray, J. D., Penedo, M. C. (2011). Mapping of equine cerebellar abiotrophy to ECA2 and identification of a potential causative mutation affecting expression of MUTYH. Genomics, 97(2), 121–129. https://doi.org/10.1016/j.ygeno.2010.11.006
Edwards L, Finno CJ. (2020). Genetics of Equine Neurologic Disease. Vet Clin North Am - Equine Pract. 36(2):255-272. doi:10.1016/j.cveq.2020.03.006