Genetic basis of e3 allele - is a loss-of-function mutation in the MC1R gene responsible for pale/yellow/white coat coloration in Arctic breeds such as Alaskan Malamutes and Siberian Huskies. The specific mutation is a 2-base pair deletion (c.816_817delCT) in the MC1R coding sequence. This deletion causes a frameshift that alters the protein, removing the last transmembrane domain and cytoplasmic C-terminal tail, resulting in a non-functional MC1R receptor. Inherited as a recessive allele, dogs homozygous for e3 or compound heterozygous for e3 and another loss-of-function allele (such as e1) express the pale or white coat color
Pathophysiology - The non-functional MC1R receptor cannot stimulate eumelanin (black/brown pigment) production. As a result, melanocytes produce only phaeomelanin, the red/yellow pigment, resulting in a cream, pale yellow, or white coat. The e3 allele causes a more extreme pale or white phenotype compared to other recessive red alleles.
Complications - No health issues are directly associated with the e3 allele. The allele only affects pigmentation, not other physiological traits.
Clinical Presentation - Dogs with e3/e3 or e1/e3 genotypes exhibit white or very pale yellow coats, often seen in Arctic breeds. Coat color can be pure white or a light cream tint, providing camouflage and adaptation to snowy environments. Other coat patterns are suppressed by the recessive loss of MC1R function.
Inheritance - The e3 allele is recessive, requiring two copies (homozygous) for full expression of pale coat color. Dogs with one copy of e3 and one copy of functional E alleles will display eumelanin-based pigmentation (i.e., black or brown colors). The e3 allele combines with other recessive alleles (e.g., e1) to influence phenotype in compound heterozygotes.
Why This Matters to Breeders and Vets - The discovery and characterization of the e3 allele enhance understanding of coat color genetics in Arctic dog breeds. Accurate genetic testing for e3 helps breeders predict coat colors, avoid surprises, and maintain breed standards. Understanding recessive alleles at the MC1R gene clarifies the molecular basis of diverse coat color phenotypes.
