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Grey
| Acronym: | Grey |
| Gene: | STX17 |
| Mutation: | 4.6kb duplication |
| Inheritance: | Autosomal Dominant |
| 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. The gray coat color in horses is not considered a base coat color and it is not present since birth meaning horses that inherit progressive gray can be born in any color. The gray gene shows progressive depigmentation of the hair, often resulting in a color that is almost completely white by 6-8 years of age. Like other coat traits, a mutation that causes gray coat color also has a pleiotropic effect meaning it may also cause some other traits or defects, dermal melanomas in this case. Gray horses have a high incidence of dermal melanomas that are commonly seen around the tail and head. The cause of the gray coat color is a 4.6 kilobases duplication within the syntaxin 17 (STX17) gene. STX17 encodes a protein that plays an important role in the production of melanocytes.
Grey coat color in horses has an autosomal dominant mode of inheritance. That means even horses with one mutated STX17 gene will show progressive greying of their coat. Research indicates that horses with one copy of gray often retain some of the original pigment while horses with two copies of gray tend to progress to almost completely white. 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 |
Normal coat |
Horse does not have the gene with the mutation and will have a normal coat. |
Gray - Carrier of normal |
Horse has one copy of the gene with the mutation and will progressively turn gray. |
Gray |
Horse has two copies of the gene with the mutation and will progressively turn gray. |
References:
Sundström, E., Imsland, F., Mikko, S., Wade, C., Sigurdsson, S., Pielberg, G. R., Golovko, A., Curik, I., Seltenhammer, M. H., Sölkner, J., Lindblad-Toh, K., Andersson, L. (2012). Copy number expansion of the STX17 duplication in melanoma tissue from Grey horses. BMC genomics, 13, 365. https://doi.org/10.1186/1471-2164-13-365
Curik, I., Druml, T., Seltenhammer, M., Sundström, E., Pielberg, G. R., Andersson, L., Sölkner, J. (2013). Complex inheritance of melanoma and pigmentation of coat and skin in Grey horses. PLoS genetics, 9(2), e1003248. https://doi.org/10.1371/journal.pgen.1003248
Rosengren Pielberg, G., Golovko, A., Sundström, E., Curik, I., Lennartsson, J., Seltenhammer, M. H., Druml, T., Binns, M., Fitzsimmons, C., Lindgren, G., Sandberg, K., Baumung, R., Vetterlein, M., Strömberg, S., Grabherr, M., Wade, C., Lindblad-Toh, K., Pontén, F., Heldin, C. H., Sölkner, J., … Andersson, L. (2008). A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. Nature genetics, 40(8), 1004–1009. https://doi.org/10.1038/ng.185