Androgen Insensitivity Syndrome (AIS)
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→ Infertility and external female genitalia in male horses.
Instructions for ordering:
- Enter the information of the first horse for which you want to order the test
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- Enter the information for a second horse
- For sample collection follow the instructions here.
- You can use this template to send in hair samples.
- Please also send the completed order form together with the samples.
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- Affected foals appear like normal females.
- Underdeveloped male and female genitalia result in infertility.
- Retained testicles are usually surgically removed.
- A malfunction of androgen receptor (male steroid hormone) causes the syndrome.
- No other effects on health of affected horses are known.
- Affected horses (genotypic males) have external female genitalia.
- Underdeveloped uterus and underdeveloped, retained testes
- Stereotypically male-like behavior
Inheritance and Genotypes
→ AIS is an X-chromosomal recessive disease, meaning that females with one copy of the genetic variant (Xais/X) are clinically normal carriers while males with one copy of the genetic variant (Xais/Y) are affected.
|Genotype:||The horse is:||Effects:|
|X/X||a normal mare.||The horse does not have any copies of the genetic variant causative for AIS and therefore cannot pass it on to any offspring.|
|Xais/X||a carrier female.||The mare is clinically healthy. The genetic variant will be passed on to its offspring with a probability of 50%. If the variant is passed on to male offspring, the foal will be an affected male.|
|X/Y||a normal male.||The male has no genetic variant causative for the AIS.|
|Xais/Y||an affected male.||The male appears to be a normal female but has the male genotype (XY) and is infertile.|
- Offspring of a carrier female should be tested for their genotype (X/X or Xais/X or Xais/Y → affected male).
- Carrier females (Xais/X) may be used for breeding but their male offspring have a 50% of being affected.
- Affected males are infertile but otherwise healthy.
Révay, T., Villagómez, D.A., Brewer, D., Chenier, T., King, W.A.: GTG mutation in the start codon of the androgen receptor gene in a family of horses with 64,XY disorder of sex development. Sex Dev 6:108-16, 2012. Pubmed reference: 22095250. DOI: 10.1159/000334049.
Further information are available at Online Mendelian Inheritance in Animals.