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Snowdrop
| Acronym: | Snowdrop |
| Gene: | SLC45A2 (MATP) |
| Mutation: | c.305G>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 breeders value and they are often caused by a variant in genes responsible for pigment synthesis. Several genes are known to diminish the intensity of the coloration and cause “dilutions”. One of those dilutions is Snowdrop dilution characterized by a dilution of both red and black pigment, so that the basic colors chestnut, bay, and black are brightened by this gene variant. This type of dilution has been previously identified in Gypsy and Tinker horse breeds. The cause of the snowdrop dilution in horses is a single nucleotide change within the MATP gene, also known as the SLC45A2 gene, the same gene whose variants cause other horse dilutions such as Cream, Pearl, or Sunshine. MATP or SLC45A2 encodes a protein that plays an important role in disrupting the trafficking of pigment molecules to developing melanocytes or pigment-producing cells. The snowdrop mutation is likely to impact the function of the SLC45A2 protein as a membrane-associated transporter.
Snowdrop dilution in horses is inherited as an autosomal recessive trait meaning two copies of the mutated gene are required for a horse to have a snowdrop or white coat color. One mutated gene will not change the coat color of black, bay, or chestnut horses, but two mutated genes will cause a snowdrop 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 |
Normal coat color |
Horse does not have the gene with the mutation and has a normal coat color. |
Normal coat color - carrier of Snowdrop dilution |
Horse has one copy of the gene with the mutation and has a normal coat color. |
Snowdrop dilution |
Horse has two copies of the gene with the mutation and displays a diluted coat color. |
References:
Bisbee, D., Carpenter, M. L., Hoefs-Martin, K., Brooks, S. A., Lafayette, C. (2020). Identification of a novel missense variant in SLC45A2 associated with dilute snowdrop phenotype in Gypsy horses. Animal genetics, 51(2), 342–343. https://doi.org/10.1111/age.12913
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