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Androgen Insensitivity Syndrome AIS


Androgen Insensitivity Syndrome (AIS)


Gene or region: AR

Reference allele: A

Mutant allele: G

Affected Breeds: Quarter Horse


Research Confidence:                             High confidence, findings supported by other species



What it does:

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.




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


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