Dark mask

The dark mask trait refers to the more intense pigmentation of the coat covering the eyes and muzzle.

Definition

The dark mask trait is represented as a darker colouration of the coat covering the eyes and mainly the muzzle, as a consequence of the expression of black pigment (eumelanin) in these areas of the face. The variant is located in the MC1R gene (also known as the extension locus or E locus) which is involved in the switch from pheomelanin (red/yellow pigment) to eumelanin production in melanocytes. Therefore, the MC1R gene is also involved in determining the dark colour of the entire coat of the dog.

Genetic basis

The dark mask variant is also known as "Em" located at the MC1R gene or E locus. The presence of one or two copies of the c.790A>G variant will increase the likelihood of expressing the dark mask phenotype, as it is a dominant trait. In the case where the dog's coat colour is dark, the trait may be unrecognisable.

Other relevant information

The final colouring of the trait may not always be black, as other variants such as those located at loci B and D may modify the production or appearance of the eumelanin pigment. In some puppies a dark mask-like appearance sometimes appears, which usually disappears in the first weeks or months of life. In this case, this phenotype is not a consequence of the "Em" variant. The trait may be called by other names such as mask or melanistic mask. The trait commonly appears in breeds such as American Bulldog, Belgian Malinois, Bloodhound, Boerboel, Boxer, Bullmastiff, German Shepherd Dog, Norwegian Elkhound, Pug, Rhodesian Ridgeback and Soft Coated Wheaten Terrier.

Bibliography

Schmutz SM, Berryere TG, Ellinwood NM,et al. MC1R studies in dogs with melanistic mask or brindle patterns. J Hered. 2003 Jan-Feb;94(1):69-73.