Cerebellar Abiotrophy (CA)
Gene or Region: MUTYH
Reference Variant: C
Mutant Variant: T
Affected Breeds: Arabian and Other Breeds
Research Confidence: High Confidence - Findings reproduced in multiple studies
Explanation of Results: ca/ca = homozygous for Cerebellar Abiotrophy, trait expressed ca/n = heterozygous for Cerebellar Abiotrophy, carrier n/n = no variant detected
General Description for Cerebellar Abiotrophy
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.
Here is a video taken at the University of Zurich in 1992 of a CA/CA foal.
Gene Information
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.
References
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
More Horse Health
Impaired Acrosomal Reaction
Impaired Acrosomal Reaction Subfertility (IAR) causes sub- or infertility in males. In normal fertilization, the the head of a sperm binds to the egg and releases the contents of a structure known as the acrosome. However, some males with IAR are unable to properly carry out this process.
Junctional Epidermolysis Bullosa
Junctional Epidermolysis Bullosa (JEB), 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, detatchment of the hooves, and oral ulcers. As there is no treatment, affected foals are humanely euthanized.
Kissing Spines Susceptibility Risk
Kissing Spines Susceptibility (KSS) evaluates a horses genetic risk for developing Kissing Spines. Horses diagnosed with Kissing Spines will have two or more dorsal spinous processes that are too close together, touch, or even overlap. This bone-on-bone grinding causes varying degrees of pain, and thus decreased mobility.
Lavender Foal Syndrome
Lavender foal syndrome (LFS), also known as coat color dilution lethal, is a neurological dysfunction in newborn foals. Symptoms are apparent at birth and include seizures, severe hyper-extension of limbs, neck and back, stiff paddling leg movements, involuntary eye movement and inability to stand or sit upright. The coat usually has a dilute color that ranges in shade from silver to a pale lavender/pink. As there is no treatment, affected foals are humanely euthanized.