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Tobiano
| Acronym: | Tobiano |
| Gene: | Eca3 |
| Mutation: | inverzija 43 Mb |
| Inheritance: | Autosomal Dominant |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Tobiano is a dominant is a part of a larger group of white spotting patterns caused by mutations in the KIT gene in humans and other animals, including horses. There are up to 30 „W“ mutations that are currently known in horses and all are breed or line specific, having originated in one specific horse. All mutations in the KIT gene affect different signaling pathways influencing the development, migration, and proliferation of melanocytes. Tobiano is characterized by patches of white that typically cross the topline somewhere between the ears and tail and it has been previously described in many different horse breeds. It is caused by a large paracentric chromosome inversion on horse chromosome 3 (ECA3) downstream of the KIT gene. This inversion may disrupt regulatory sequences for the KIT gene and cause the white spotting pattern.
This type of white spotting pattern in horses is inherited as an autosomal dominant trait. That means even horses with only one mutated gene will develop white spotting. Horses carrying Tobiano mutation can show other characteristics such as dark head, with white markings like those of a solid-colored horse, white legs below the hocks and knees and tails in two colors. 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 color |
Horse does not have the gene with the mutation and has a normal coat color. |
Tobiano pattern - Carrier of normal |
Horse has one copy of the gene with the mutation and displays a Tobiano pattern. |
Tobiano pattern |
Horse has two copies of the gene with the mutation and displays a Tobiano pattern. |
References:
Brooks, S., Lear, T., Adelson, D., Bailey, E. (2007). A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses. Cytogenetic and Genome Research, 119(3-4), 225-230. https://doi.org/10.1159/000112065
Haase, B., Jude, R., Brooks, S. A., Leeb, T. (2008). An equine chromosome 3 inversion is associated with the tobiano spotting pattern in German horse breeds. Animal genetics, 39(3), 306–309. https://doi.org/10.1111/j.1365-2052.2008.01715.x