Genetic basis of Eg allele - is a variant of the MC1R gene at the E locus, specifically a mutation c.233G>T. It modifies coat color by reducing eumelanin (black/brown pigment) and increasing phaeomelanin (red/yellow pigment) production. This allele is responsible for the grizzle (or domino) coat color phenotype in several sighthound breeds, including Salukis, Borzois, Polish Greyhounds, and Afghan Hounds. The Eg allele is recessive to the melanistic mask (Em) and normal E allele but dominant over recessive red (e).
Pathophysiology - The mutation alters MC1R receptor function, impacting pigment synthesis in hair follicles. Dogs with eg/eg or eg/e1 genotypes show grizzle coloration due to partial reduction in eumelanin and increased pheomelanin. The phenotype is influenced by other coat color loci such as A (agouti) and K (dominant black). Grizzle typically appears as a blend of light and dark hairs creating a speckled or “salt and pepper” or shaded coat effect.
Complications - No known health implications linked to the Eg allele. The allele affects only coat color and pattern.
Why This Matters to Breeders and Vets - Understanding the Eg allele helps breeders predict grizzle or domino coat patterns in sighthound breeds and others. It aids in clarifying sometimes confusing coat color phenotypes caused by interactions of E locus alleles. Facilitates accurate genetic testing and breeding decision-making to maintain or avoid the grizzle pattern.