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
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