Grizzle coat

The grizzle coat is a typical coat trait of Saluki, Borzoi and Afghan Houndsun dogs characterized by a mixture of light and dark colors.

Definition

The grizzle trait is characterized by a coat resulting from a mixture of light and dark colors, with a darker intensity of coloration on the forehead than on the rest of the body. The variant responsible for the trait 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 (black/brown pigment) production in melanocytes. Thus, the MC1R gene is also involved in determining the dark color of the entire coat of the dog.

Genetic basis

The grizzle trait is also known as the "Eg" allele. The type of inheritance is dominant, therefore, the presence of one or two copies of the c.233G>T variant will allow the expression of the grizzle phenotype. For this trait to be expressed, it is necessary that the variant responsible for the dark mask trait is not present, as this genotype is dominant to the grizzle trait genotype. In addition, the final colouring of the dog may differ depending on the variant present at loci A, B and K.

Other relevant information

The grizzle phenotype is the result of a reduced function variant of the MC1R gene, thus the variant limits the amount of eumelanin but does not inhibit all eumelanin synthesis. The trait is found in many Sighthound breeds and is therefore often seen in combination with the tan spotted coat pattern that is very common in these breeds. This trait is known as "grizzle" in the Saluki breed, "sable" in the Borzoi and "domino" in the Afghan Hounds. These three breeds are the ones that commonly present the grizzle trait.

Bibliography

Dreger DL, Schmutz SM. A new mutation in MC1R explains a coat color phenotype in 2 "old" breeds: Saluki and Afghan hound. J Hered. 2010 Sep-Oct;101(5):644-9.