Androgen Insensitivity Syndrome in a Family of Warmblood Horses Caused by a 25-bp Deletion of the DNA-Binding Domain of the Androgen Receptor Gene.

This research explores a genetic condition known as Androgen Insensitivity Syndrome (AIS) in a pedigree of Warmblood horses. The researchers identified a specific 25-base pair deletion in the DNA-binding domain of these horses’ androgen receptor gene, which they found to be the cause of the syndrome.

About Androgen Insensitivity Syndrome in Horses

• Androgen Insensitivity Syndrome (AIS) in horses is a genetic condition referred to in previous research as testicular feminization.
• It occurs due to the failure of androgen secretions to masculinize target organs during a horse’s embryonic development.
• The syndrome results in animals that have a female phenotype (physical appearance) but a male genotype.
• The genotype of an AIS horse is characterized as 64,XY SRY+, indicating the presence of a male-specific gene on the Y chromosome.

Inheritance Pattern

• The pathological condition of AIS is proposed to follow an X-linked recessive pattern of inheritance in some horse breeds.
• This means that the trait associated with AIS is carried on the X chromosome and must be inherited from both parents to manifest in offspring.
• The documented study took place in a pedigree of Warmblood horses, a breed previously unstudied in this context.

The 25-bp Deletion and AIS

• The research found a direct link between a specific 25-base pair deletion in the DNA-binding domain of the androgen receptor gene and the occurrence of AIS in the Warmblood horse family.
• A 25-base pair deletion means that a sequence of 25 base pairs is missing from a particular area of the gene.
• The DNA-binding domain of the androgen receptor gene is crucial for the binding of androgens, which stimulate the development of male characteristics. The deletion in this area disrupts the gene’s functionality, leading to AIS.