Androgen insensitivity syndrome / AIS (AR1-related) - Horse

What does this test examine?

This genetic test examines the AR c.1A>G variant, also known as AR1, in horses. The condition is described as androgen insensitivity syndrome, AIS, testicular feminization and 64,XY disorder of sex development.

What does this mean for the horse?

The AR gene encodes the androgen receptor. This receptor is needed for the developing body to respond properly to male hormones. In a genetic male horse with the AR1 variant, this signalling pathway is impaired. As a result, male sexual development does not proceed normally, while the horse may appear phenotypically female and may have internal testicular tissue.

AIS is especially relevant in fertility problems, unexpected sex development or breeding decisions in lines where the variant occurs. A genetically male affected horse is expected to be sterile. Mares with one copy are carriers and can pass the variant to some offspring.

Practical value of this test

• The test detects the known AR1 variant c.1A>G in the androgen receptor gene.
• The result helps identify carrier animals before breeding decisions are made.
• In atypical or unclear sex development, the DNA result provides focused genetic clarity.
• Breeders can plan matings more effectively to avoid affected foals.

Inheritance and result

This variant is inherited as an X-linked recessive trait. Female animals have two X chromosomes and can be carriers. Male animals have one X chromosome; when a genetic male foal inherits the AR1 variant, it causes AIS with androgen insensitivity, female-appearing external characteristics and infertility.