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E locus - Chestnut
| Acronym: | Chestnut |
| Gene: | MC1R |
| Mutation: | c.248C>T, c.250G>A |
| 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 that are caused by variants in genes responsible for either the melanocyte or the pigment synthesis or its combinations. However, there are three base coat colors in horses and they include black, bay, and chestnut (also referred to as sorel or red). The chestnut color is under the control of the extension gene, also known as the E locus or red factor which is mostly concerned with the production of black pigment. When the E locus that encodes melanocyte-stimulating hormone receptor (MC1R) is mutated and non-functional, yellow pigments predominates because the black one cannot be produced and a horse with a chestnut coat color is the result. If the MC1R protein is functional, it enables the production of black pigment—eumelanin and hence, black pigment predominates and the horse has a black coat.
Chestnut coat color in horses is inherited as an autosomal recessive trait meaning two copies of the mutated E locus gene are required for the red color to appear. Horses with two copies of the variant of the MC1R gene will have a red coat base color due to the non-functional protein for black pigment synthesis. Horses with one copy or no copies of the mutated MC1R gene will most likely have a black base color. Genetic testing can identify carriers and help breeders in future mating pairs selection.
Results Reported As
Test Result |
Interpretation of test result |
Bay or black coat color |
Horse does not have the gene with Chestnut associated mutation. Horse will have bay or black coat color. |
Bay or black coat color - carrier of Chestnut |
Horse has one copy of the gene with Chestnut associated mutation. Horse will have bay or black coat color. |
Chestnut coat color |
Horse has two copies of the gene with Chestnut associated mutation. Horse will have Chestnut coat color. |
References:
Marklund, L., Moller, M. J., Sandberg, K., Andersson, L. (1996). A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses. Mammalian genome : official journal of the International Mammalian Genome Society, 7(12), 895–899. https://doi.org/10.1007/s003359900264
Wagner, H. J., Reissmann, M. (2000). New polymorphism detected in the horse MC1R gene. Animal genetics, 31(4), 289–290. https://doi.org/10.1046/j.1365-2052.2000.00655.x
Shang, S., Yu, Y., Zhao, Y., Dang, W., Zhang, J., Qin, X., Irwin, D. M., Wang, Q., Liu, F., Wang, Z., Zhang, S., Wang, Z. (2019). Synergy between MC1R and ASIP for coat color in horses (Equus caballus)1. Journal of animal science, 97(4), 1578–1585. https://doi.org/10.1093/jas/skz071