Mushroom (Dilution factor Horse)
Mushroom is a coat colour unique to the Shetland Pony, where phaeomelanin (chestnut colour) is lightened to a light sepia shade. Mushroom can also slightly affect the coat colour of ponies with bay base colour.
The colour is inherited autosomal recessively. Animals with one copy of the mutation (N/mu) show no dilution. Only animals with two copies of the mutation (mu/mu) show the Mushroom dilution.
Genetic Test: available in Shop
- Mushroom is a coat colour phenotype in the Shetland Pony.
- Reduced production of pheomelanin (red pigmentation) dilutes chestnut colour to a light sepia tone.
- Near white mane and tail.
- The base colour bay can be slightly affected by Mushroom.
- Horses with base colour black are not affected, but can pass the variant on to the offspring.
Genotype and Lab Report
Inheritance: autosomal recessive
→ Only animals with two copies of the Mushroom factor (mu/mu) show the Mushroom dilution.
N/N = No Mushroom mutation
The horse does not show the diluted coat colour.
N/mu = One copy of the Mushroom variant, carrier
The horse does not show the diluted coat colour. The genetic variant will be passed on to the offspring with a probability of 50%.
mu/mu = Two copies of the Mushroom variant
The horse shows the Mushroom dilution, if the base colour is chestnut (or bay). The genetic variant will be passed on to the offspring with a probability of 100%.
Tanaka J et al. (2019). Genome Wide Association Study Identifies Locus for the Mushroom Coat Color Dilution in Shetland Ponies. XXVII Plant and Animal Genome Conference, San Diego. Abstract number W359.
Tanaka, J., Leeb, T., Rushton, J., Famula, T.R., Mack, M., Jagannathan, V., Flury, C., Bachmann, I., Eberth, J., McDonnell, S.M., Penedo, M.C.T., Bellone, R.R.: Frameshift Variant in MFSD12 Explains the Mushroom Coat Color Dilution in Shetland Ponies. Genes (Basel) 10:, 2019. Pubmed reference: 31635058. DOI: 10.3390/genes10100826.
Further information is available at Online Mendelian Inheritance in Animals.