Genetic basis of eA allele - is a novel variant of the MC1R gene (E locus), called “Ancient Red” (eA). It results from a missense mutation R301C in the MC1R gene. The MC1R gene controls the type of pigment produced: eumelanin (black/brown) or pheomelanin (red/yellow). The eA allele is recessive to the wild-type E allele (which allows dark pigment) but dominant to the common recessive e allele (responsible for solid red/yellow coloring). This allele is found primarily in Spitz breeds (e.g., Alaskan Malamute, Siberian Husky) and some Scent hounds (e.g., Beagle).
Pathophysiology - Dogs with eA produce a unique coat pattern characterized by partial expression of eumelanin and pheomelanin, resulting in coat colors that are often called domino, grizzle, or pied. The eA allele reduces dark pigment production, affecting typical coat patterns controlled by other loci (K and A loci). Dogs with homozygous eA/eA or heterozygous eA/e genotypes produce patterns such as: Domino in Alaskan Malamutes and other Spitz breeds, Grizzle in Chihuahuas, Pied in Beagles. Unlike the e allele, which causes solid recessive red/yellow, the eA variant produces distinctive patterned coats with partial eumelanin presence
Complications - No known health complications are directly related to the eA allele. Phenotypic effects are limited to coat color and pattern expression.
Clinical Presentation - Coat colors include typical domino or grizzle patterns, with red or yellow background colors and varying degrees of darker shading. Patterns are breed-specific but generally recognisable by the distribution of light and dark areas on the coat. Dogs with eA may show more diverse and intricate coat coloring than typical recessive red dogs.
Inheritance - The eA (Ancient Red) allele is recessive to E but dominant to e, giving it a unique position in the E locus dominance hierarchy: E > Em (melanistic mask) > EG (grizzle/domino) > eA (ancient red) > e (recessive red) This means that if a dog carries eA and E, the dog will have dark pigmentation; if it carries eA and e, the eA pattern will be expressed. eA requires two copies (homozygous) or one copy with e to express its phenotype.
Why This Matters to Breeders and Vets - The discovery of eA refines understanding of coat color genetics and explains coat patterns that did not fit prior models. Helps breeders and geneticists better predict and describe coat colors in affected breeds. It provides insight into ancient dog pigmentation genetics, linking modern breeds to early domesticated dogs.