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Mushroom Dilution
| Acronym: | MD |
| Gene: | MFSD12 |
| Mutation: | c.600dupC |
| 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 Mushroom Dilution responsible for the dilution of the chestnut coat color to a sepia tone in Shetland Ponies. The cause of the mushroom coat color is duplication within the MFSD12 gene encoding the major facilitator superfamily domain containing 12 protein. MFSD12 has been reported to be highly expressed in melanocytes relative to other cell types including keratinocytes and it plays an integral role in trafficking transmembrane solutes and determining the quantity of eumelanin and pheomelanin produced. The mushroom phenotype shows wide variation in shade and has similarities to cream and silver dilutions. The body shade can range from a lighter yellow, appearing similar to cream dilution on a chestnut background (palomino), to a deeper taupe shade, phenotypically similar to horses carrying the silver allele.
Mushroom Dilution in Shetland Ponies has an autosomal recessive mode of inheritance. That means the pony must have two copies of the mutated genes to dilute to mushroom coat color. Horses with only one copy of the mutated gene will not show dilution. Horses with two specific mutations within the MFSD12 gene may also show other characteristics such as a flaxen mane and tail. 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 Mushroom dilution |
Horse has one copy of the gene with the mutation and has a normal coat color. |
Mushroom dilution |
Horse has two copies of the gene with the mutation and displays a diluted coat color. |
References:
Tanaka, J., Leeb, T., Rushton, J., Famula, T. R., Mack, M., Jagannathan, V., Flury, C., Bachmann, I., Eberth, J., McDonnell, S. M., Penedo, M., Bellone, R. R. (2019). Frameshift Variant in MFSD12 Explains the Mushroom Coat Color Dilution in Shetland Ponies. Genes, 10(10), 826. https://doi.org/10.3390/genes10100826
Tanaka, J.L., Leeb, T., Mack, M., Jagannathan, V., Flury, C., Bachmann, I., McDonnell, S., Penedo, M.C., Bellone, R.R.: A frameshift variant in MFSD12 explains the mushroom coat Color dilution in Shetland Ponies. PAG XXVII :W355, 2019.