G-Locus Horse (Grey)

G-Locus Horse (Grey)

In horses, the gene for syntaxin 17 (STX17) is known as the Grey Locus (G-locus). A dominant mutation to this gene results in the gradual development of a grey coat. The mutation causes progressive depigmentation (fading) of the hair and is considered to be the “strongest” of all coat colour modifying genes, ultimately overriding most other coat colours. The depigmentation process may last for years, but once the hair is depigmented, the original colour will never return.

Horses affected by the mutation may be born any colour. However, the coat greys as the horse matures, typically starting around the face and flanks. As depigmentation progresses, it often results in a dappled pattern for a period of time, which may be mistaken for a roan coat. Some horses may also develop darker speckles, particularly if they are only carriers for the mutation.

Complex mutation

Due to the complex nature of the mutation, test P807 cannot distinguish between horses that are homozygous or heterozygous for the mutation. It can only determine whether the horse has at least one copy.

Relevant tests

• P807