Dark/Light Pigment (E Locus)

General Information: The E Locus (e), determined by the MC1R gene, plays a pivotal role in the coat color of dogs by dictating whether melanocytes produce black or brown pigment (eumelanin) or yellow or red pigment (phaeomelanin). This locus contains multiple alleles such as E (dominant, leading to the production of dark pigments), e1, e2, e3 (all leading to lighter, yellow or red coats), and Em (causing a melanistic mask). The phenotype expressed by a dog not only depends on the E locus alleles but also on other genetic factors from the A, B, and K loci, influencing color distribution and type. For instance, the Em allele will produce a dark mask on the face, while homozygous e alleles will lead to yellow or red coats without any dark pigment.

Gene / Testing Information: Genetic testing of the E Locus (e) is crucial for breeders to understand and predict the coat color outcomes in offspring, as it examines variations in the MC1R gene linked to different coat color expressions. This testing helps identify whether a dog carries alleles like E, e1, e2, e3, or Em, each influencing the coat color in distinct ways. Since the E allele is dominant, dogs with one or two copies will show dark pigment unless affected by other loci. Carriers of the e alleles (e1, e2, e3) can produce lighter-colored offspring if both parents contribute a recessive e allele. Such insights allow breeders to make informed decisions to achieve desired coat colors or avoid unwanted combinations in future litters, enhancing genetic health and diversity within the breed lines.