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A locus (Bay/Black)
| Acronym: | AGOUTI |
| Gene: | ASIP |
| Mutation: | c.191_201del |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Horses display a huge variety of distinct coat color patterns and those variations in coat and skin colors are likely caused by changes in genes responsible for either the melanocyte or the pigment synthesis or its combinations. The agouti gene controls the distribution of black pigment and determines whether a horse will have a bay or black base coat color. The agouti gene is also known as locus A and it encodes the agouti-signaling-protein (ASIP) that controls the relative amounts of melanin pigments in mammals. A mutation in the Agouti gene results in a loss-of-function protein that causes extended production of black pigment—eumelanin and hence, black pigment predominates and the horse has a black coat. If the gene encodes a functional protein, ASIP restricts the black pigment synthesis and yellow pigment predominates resulting in a bay or reddish-brown color.
Black coat color in horses is determined by two loci, A and E. If the E locus is normal, the black coat color is inherited as an autosomal recessive trait meaning the horse must carry two mutated Agouti genes for the black base color to develop. Horses with only one mutated gene or no mutated genes will develop bay or reddish-brown coat color. Early detection by genetic testing can help identify carriers of the mutation and help breeders in further selection of mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
Bay coat color * |
Horse does not have the gene with Agouti associated mutation. Horse will have bay base coat color. |
Bay coat color - carrier of black * |
Horse has one copy of the gene with Agouti associated mutation. Horse will have bay base coat color. |
Black coat color * |
Horse has two copies of the gene with Agouti associated mutation. Horse will have black base coat color. |
* if there is no mutation in the E locus - Chestnut
References:
Rieder, S., Taourit, S., Mariat, D., Langlois, B., Guérin, G. (2001). Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses (Equus caballus). Mammalian genome : official journal of the International Mammalian Genome Society, 12(6), 450–455. https://doi.org/10.1007/s003350020017
Castle W. E. (1948). The Abc of Color Inheritance in Horses. Genetics, 33(1), 22–35. https://doi.org/10.1093/genetics/33.1.22