Silver | Dapple (Dilution factor Horse)
The Silver mutation leads to the lightening of the mane and tail while the body coat remains relatively dark due to the reduced storage of the dark colour pigment "eumelanin" in the (long) hair.
Therefore, only horses with the base colour black or bay show the lightening, while horses with the base colour chestnut (only light colour pigment phaeomelanin) may be carriers of the silver mutation.
The mutation is associated with eye problems called Multiple Congenital Ocular Abnormalities (MCOA).
Genetic Test: available in Shop
Also in the Dilution package
General Information
- Silver results in the decreased storage of the black pigment “eumelanin” in hair.
- The mane and tail of Silver horses (base colour black or bay) are usually of lighter colour than the coat (stays dark) → may lead to confusion with “Flaxen” or dark chestnut colours.
- Horses with a Chestnut base colour may be carriers for the Silver mutation but do not develop the diluted coat colour themselves.
Associated disease
Multiple Congenital Ocular Abnormalities (MCOA)
The Silver mutation is associated with eye problems in some breeds. Horses with one copy of the variant (n/Z) may have a milder form of MCOA while homozygous horses (Z/Z) may develop more severe symptoms.
Test Information
Locus Information: Z-Locus
This test detects a missense mutation (g.73665304C>T) in the PMEL17 gene.
Test in Shop
Genotype and Lab Report
Inheritance: autosomal-dominant
→ Horses with only one copy of the variant (n/Z) will show the same phenotype as horses with two copies of the variant (Z/Z).
→ The eye problem Multiple Congenital Ocular Abnormalities (MCOA) associated with Silver in some breeds is incomplete autosomal dominant, horses with two copies may be at higher risk of developing 'Multiple Congenital Ocular Abnormalities' (MCOA)
Genotype
n/n = No copy of the Silver variante
The horse does not show no dilution of mane and tail
n/Z = One copy of the Silver variante
The horse is silver, black silver or brown silver depending on the base colour.
Z/Z = Two copies of the Silver variante
The horse is silver, black silver or brown silver depending on the base colour. It may be at higher risk of developing 'Multiple Congenital Ocular Abnormalities' (MCOA).
Appearance
Silver/Dapple
A black horse influenced by the Silver mutation.
Mane and tail are very light, almost white. The body remains relatively dark.
E*aa n/Z or E*aa Z/Z
Silver/Dapple (Bay)
A bay horse influenced by the Silver mutation.
Mane and tail are very light, almost white. The body remains brown.
A bay silver horse can be confused with dark chestnut colours and 'Flaxen'.
E*A* n/Z or E*A* Z/Z
Literature
Brunberg, E., Andersson, L., Cothran, G., Sandberg, K., Mikko, S., Lindgren, G.: A missense mutation in PMEL17 is associated with the silver coat color in the horse. BMC Genetics 7:46, 2006. Doi: 10.1186/1471-2156-7-46.
Andersson, L.S., Wilbe, M., Viluma, A., Cothran, G., Ekesten, B., Ewart, S., Lindgren, G.: Equine Multiple Congenital Ocular Anomalies and Silver Coat Colour Result from the Pleiotropic Effects of Mutant PMEL. PLoS One 8:e75639, 2013. Doi: 10.1371/journal.pone.0075639.
Further information is available at Online Mendelian Inheritance in Animals.