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Sunshine
| Acronym: | Sunshine |
| Gene: | SLC45A2 (MATP) |
| Mutation: | c.568G>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 Sunshine dilution which causes lightening of the coat, mane, and tail color of the horse. Sunshine coat color is visually very similar to the Pearl dilution creating a pseudo-double dilute effect and is located on the same gene as the Cream dilution factor. It has been firstly detected in a horse cross breed Standardbred x Tennessee Walking Horse. The cause of the Sunshine dilution in horses is a single base pair 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 Snowdrop. 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.
Sunshine 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 sunshine coat color. However, a sunshine gene may interfere with other SLC45A2 mutations. Only animals with two copies of the Sunshine factor or animals with one copy of “Sunshine” in combination with one copy of “Cream” show the Sunshine dilution. 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 Sunshine dilution |
Horse has one copy of the gene with the mutation and has a normal coat color. |
Sunshine dilution |
Horse has two copies of the gene with the mutation and displays a diluted coat color. |
References:
Holl, H. M., Pflug, K. M., Yates, K. M., Hoefs-Martin, K., Shepard, C., Cook, D. G., Lafayette, C., Brooks, S. A. (2019). A candidate gene approach identifies variants in SLC45A2 that explain dilute phenotypes, pearl and sunshine, in compound heterozygote horses. Animal genetics, 50(3), 271–274. https://doi.org/10.1111/age.12790