Test Detail

Test for the silver allele (silver dapple) of the PMEL gene, which lightens the black pigment of the mane and tail and of the dark areas of the coat. It detects the associated variant and its pleiotropic effect on ocular development. Complementary to, not a substitute for, clinical and ophthalmological examination.

Applicable breeds: Icelandic Horse, Miniature Horse, Rocky Mountain Horse, Shetland Pony, Morgan, Comtois and others. Frequencies: limited data.

• Lightening of the mane and tail and, to a lesser degree, of the black coat, towards silver-grey or white.\n• No visible effect on chestnut (phaeomelanic) coats.\n• In homozygosity it is associated with congenital ocular anomalies (MCOA), with cysts and anterior segment alterations.

Silver was mapped to chromosome 6 and in 2006 Brunberg and colleagues identified the mutation in PMEL17 (now PMEL). In 2013 Andersson and colleagues demonstrated that the same variant in homozygosity causes multiple congenital ocular anomalies (MCOA).

• Avoid mating two silver carriers to reduce the risk of MCOA in homozygosity.\n• In silver foals, consider an ophthalmological examination for possible MCOA.\n• The allele does not visibly modify the chestnut coat, so it may go unnoticed.\n• Do not confuse silver with roan or with other lightening patterns.

MCOA includes ciliary cysts, iris dysplasia and iridocorneal angle anomalies. Early detection allows vision to be monitored. The variant is the same in the breeds studied.

1. Brunberg 2006, A missense mutation in PMEL17 is associated with the Silver coat color (PMID 17029645); OMIA:001438-9796.
2. Andersson 2013, Equine multiple congenital ocular anomalies and silver coat colour result from the pleiotropic effects of mutant PMEL (PMID 24086599); OMIA:001438-9796.