Cerebellar Abiotrophy (CA)
Gene or region: MUTYH
Reference allele: C
Mutant allele: T
Affected Breeds: Arabian
Research Confidence: High confidence, findings reproduced in multiple studies
What it does:
Cerebellar Abiotrophy (CA) is a degenerative neurological disorder due to the death of large neurons (Purkinje cells) in the cerebellum. Foals affected by CA begin show symptoms between 6 weeks and 4 months of age. These horses display head tremors, lack of coordination, wide stances, exaggerated gait, difficulty rising, and startle easily. As this disease is an autosomal recessive condition, a horse must inherit two copies of the allele (CA/CA) to show any signs. Horses with only one copy of the allele (CA/N) are known as carriers due to their ability to produce affected foals.
MUTYH is an enzyme that functions to repair oxidative damage, and is expressed at high levels in the brain. Although many other species are also affected by CA, the horse is the only one associated with mutations in this gene. This particular mutation is located a short distance from MUTYH, and is likely involved in its regulation.
Below is a video taken at the University of Zurich in 1992 of a CA/CA foal
Brault LS et al., “Mapping of equine cerebellar abiotrophy to ECA2 and identification of a potential causative mutation affecting expression of MUTYH.” (2011) Genomics. 97: 121-9. PMID: 21126570
Brault LS and Penedo MC, “The frequency of the equine cerebellar abiotrophy mutation in non-Arabian horse breeds.” (2011) Equine Vet J. 43: 727-31. PMID: 21496100
Cavalleri JM et al., “Morphometric magnetic resonance imaging and genetic testing in cerebellar abiotrophy in Arabian horses.” (2013) BMC Vet Res. 9: 105. PMID: 23702154
Tarr CJ et al., “The carrier prevalence of severe combined immunodeficiency, lavender foal syndrome and cerebellar abiotrophy in Arabian horses in South Africa.” (2014) Equine Vet J. 46: 512-4. PMID: 24033554
Are there similar genetic disorders in humans? Yes, unfortunately, there are children who suffer from a condition known as Acute Cerebellar Ataxia (ACA). Take a look at the video below (Ethan's Story) and notice the similarities in movement, balance and challenges experienced by these children and their families: