Androgen Insensitivity Syndrome (AIS)
Gene or Region: AR
Reference Variant: A
Mutant Variant: G
Affected Breeds: Quarter Horses
Research Confidence: High - Findings supported by other species
Explanation of Results: AIS/AIS = homozygous for Androgen Insensitivity Syndrome, not observed AIS/n (female) = heterozygous for Androgen Insensitivity Syndrome, female carrier AIS/n (male) = heterozygous for Androgen Insensitivity Syndrome, sterile and phenotypically female n/n = no variant detected
General Description
Androgen Insensitivity Syndrome (AIS), previously known as Testicular Feminization Syndrome, is a disorder of sexual development in which a horse with a XY SRY+ karyotype appears female. Horses with AIS exhibit stallion-like behaviors, have external female genitalia, and often internal un-descended testicles.
AR is a steroid-activated transcription factor that plays a key role in normal sexual development. Mutations in other species have been noted to cause AIS and have been associated with prostate cancer. This particular mutation is a single base change that alters the start codon of the encoded protein. Though normal transcription and translation still occurs, the encoded protein likes has an altered function.
References
Révay T et al., “GTG mutation in the start codon of the androgen receptor gene in a family of horses with 64,XY disorder of sex development.” (2012) Sex Dev. 6: 108-16. PMID: 22095250
More Horse Health
Recurrent Laryngeal Neuropathy
Recurrent Laryngeal Neuropathy (RLN) is a disease that results in loss of the neurons that open the larynx, significantly affecting performance in Thoroughbreds and other sport horses. It is an important issue for horses in competitive events because the resultant paralysis of the larynx leads to obstruction of air flow during intense exercise, creating the abnormal inspiratory noise that gives RLN its common name: “roaring”.
Severe Combined Immunodeficiency
Severe Combined Immunodeficiency Disease (SCID) is a condition in which affected foals are unable to mount an effective immune response after infection and are unable to recover from infections that unaffected foals would easily resist. The disease is universally fatal in horses, usually within 4-6 months of life.
West Nile Virus Symptom Susceptibility / Risk
West Nile Virus (WNV) is a mosquito-borne virus that can infect multiple types of mammals, including horses. Infection can lead to a series of severe symptoms, most commonly encephalitis – acute inflammation of the brain. Severe neurological symptoms develop in ~8% of exposed horses, and once symptoms manifest, the fatality rate ranges from 20-40% and is higher in older horses.