The Silver gene (SILV gene), also called premelanosome protein (PMEL17 gene) is responsible for Merle. This gene is also known as M-Locus. Merle only dilutes eumelanin (black) pigment; dogs with two copies of the allele e (homozygous e/e) at E-Locus have no black pigment, thus do not express merle. Merle is an incompletely dominant coat color pattern characterized by irregularly shaped patches of diluted pigment and solid color. Blue and partially blue eyes are typically seen with merle, and merle dogs often have a wide range of auditory and ophthalmologic defects. Breeds with merle coat pattern are Shetland Sheepdog, Collie, Border Collie, Australian Shepherd, Cardigan Welsh Corgi, Catahoula Leopard Dog, Dachshund, Great Dane, Bergamasco Sheepdog and Pyrenean Shepherd. The Coat Colour Merle test (H630) tests for the genetic status of the M-locus. The M-locus has three variants (alleles): M (merle, SINE with longer poly-A tail), Mc (cryptic merle, SINE with shorter poly-A tail) and N (non-merle, no SINE insertion. Dogs with cryptic merle (also called phantom or ghost merle), typically display little to no merling and some may be misclassified as non-merles.
The Coat Colour Merle test encloses the following results.
|
M-Locus |
Coat Colour |
|---|---|
|
M/M |
Merle coat colour, two copies of merle are present (double merle). Dog may exhibit auditory and ophthalmologic defects |
|
M/Mc |
Merle coat colour, One copy of merle and one copy of cryptic merle are present. Dog may exhibit auditory and ophthalmologic defects |
|
M/N |
Merle coat colour, one copy of merle is present. Dog may exhibit auditory and ophthalmologic defects |
|
Mc/Mc |
Cryptic-merle, two copies of cryptic merle are present. The dog is genetically healthy with regards to the merle factor |
|
Mc/N |
Cryptic-merle, one copy of cryptic merle is present, the dog is genetically healthy with regards to the merle factor |
|
N/N |
Non-merle, no copies of merle or cryptic merle are present, the dog is genetically healthy with regards to the merle factor |
