The E Locus in Dogs

This webpage is part of a series on Dog Coat Color Genetics and was last updated on July 26, 2020 by Sheila Schmutz, PhD. It was moved to a different server.

Clear Red

The gene known as the E locus is the Melanocortin Receptor 1 gene (MC1R), formerly called the Melanocyte Stimulating Hormone Receptor Gene (MSHr). The MC1R gene has been mapped to dog chromosome 5.

This gene has two common alleles E and e that are present in many dog breeds. Dogs that are e/e are red or yellow due to phaeomelanin production, and this is the recessive genotype. When E is present in a dog, it usually has some black or brown in its coat because of the production of eumelanin. The E allele is dominant to the e allele.

Although the e/e genotype is the most recessive at this locus, it is epistatic or masks other genotypes at other loci, such as the K and A locus. See more about those loci on separate pages.

These 2 Dachshunds exemplify two genotypes at this locus. The red dog has a black nose but is a clear red and has the genotype e/e at MC1R. The black is a black-and-tan and has an E allele, however his black-and-tan pattern is due an agouti allele (at)(see the agouti page for more details).

There are Dachshunds, such as the one shown, and dogs of other breeds that have red hairs with darker or black tips on them. These dogs do not have an e/e genotype. This non-solid red is caused by an allele at the agouti locus, ay. Other breeds such as Chows also fall into the category of not being red because of an e/e genotype. The colors tan or fawn, typically associated with agouti, are not always that easily distinguishable from the red of an Irish Setter. Depending on the breed, one red or the other is more common and in most breeds only one or the other red occurs.

In some breeds, such as Labrador Retrievers the dogs are more yellow than red. The shade varies as is illustrated by the two littermates above whose parents were also both yellow.

Little did not include the Hungarian Vizsla in his studies. They are hunting dogs which are typically gold to red and typically have brown noses because they are also homozygous for the recessive brown allele/s at the B locus. (see Brown for further details)

This very white coat color is desirable in English Setters but it makes it difficult to tell what color the pigmented part of her coat is. By MC1R testing, she is e/e and therefore red.

Breeds in which yellow-to-red dogs of the e/e genotype have been detected

Note that in some breeds dogs with an e/e genotype are more often cream to white than yellow to red (see webpage on white for a discussion of these breeds).

  • Newton, J., A. Wilkie, L. He, S. Jordan, D. Metallinos, N. Holmes, I. Jackson and G. Barsh. 2000. Melanocortin 1 receptor variation in the domestic dog. Mamm. Genome 11:24-30.
  • Everts, RE, Rothuizen,J. and van Oost,B.A. 2000. Identification of a premature stop codon in the melanocyte-stimulating hormone receptor gene (MC1R) in Labrador and Golden retrievers with yellow coat colour. Anim. Genet. 31: 194-199.
  • Schmutz, S.M., J. S. Moker, T. G. Berryere, and K. M. Christison. 2001. A SNP is used to map MC1r on dog chromosome 5. Animal Genetics 32:43-44.
  • Thomas, R., M. Breen, P. Deloukas, N. G. Holmes and M. M. Binns. 2001. An integrated cytogenetic, radiation-hybrid and comparative map of dog Chromosome 5. Mamm. Genome 12:371-3100.

  • Red in Australian Cattle Dogs and Sled Dogs: e2 and e3

    Pale red occurs rather rarely in Australian Cattle Dogs. A new mutation was found in the regulatory region of MC1R in 2018 that causes this coat color. It was only observed in this breed, although many breeds were studied. This allele was called e1 by the researchers who found it.

    Another mutation that causes a premature stop codon was discovered in northern sled dogs, such as Siberian Huskies. This allele is called e3 or edel. Dogs that have two such alleles or one of these and one e are a creamy white instead of red.

    Black versus Red

    Black, or black and white is a very common coat color in many dog breeds. It would appear that most of the hunting dogs that have black variants, such as German Shorthairs, German Wirehairs, and Pudelpointers are black because they have an E alllele at the MC1R gene. The Large Munsterlander is "always" E/E and black. However the American Brittany and the Irish Setter are always e/e and red or orange or yellow. But the Small Munsterlander and German Longhair are brown, not red, and are also E/E due to the interaction of another gene B, explained on the page about brown.

    Note that for a dog like Charlie, shown here, to be black it must also have a KB allele. KB is discussed on the page about the K locus.

    Grizzle and Domino

    There is an allele EG which was decribed for the first time in 2010. This allele is relatively common in both Salukis and Afghans Hounds but is not found in virtually any other breeds. When EG occurs in dogs with an at/at and no KB or EM allele the phenotype of grizzle, as shown in the photo of the Saluki at the right, or domino results.

    See the page about Salukis for more information.

    The manuscript describing this was published in Journal of Heredity in Fall, 2010. A free PDF copy of the manuscript is available for download

    Melanistic Mask

    There is another allele at the E locus, EM. Melanistic masks are rare in the hunting breeds, but are relatively common in many other breeds. The mask caused by this allele is not visible on solid colored dogs which are black, brown, or gray.

    EM is the top dominant allele in this series.

    Some but not all Whippets, Greyhounds, Afghans, Great Danes, French Bulldogs have black masks, which Little suggested is due to an allele at MC1R, EM. The Whippet is a pale solid color (fawn), and the Akita is sable, both with a black mask. Little suggested that masked was dominant to its absence on fawn or brindle dogs. The mutation causing mask was found in the MC1R allele by our lab.

    The mechanism by which a black mask is formed is an interaction between the MC1R or E gene with the agouti protein and melanocyte stimulating hormone. The EM allele allows agouti to bind some of the time and cause fawn pigment to be made on the body and the melanocyte stimulating hormone to bind on the face instead. Because of this any phaeomelanin pigmented dog (i.e. yellow, fawn, red, cream) with a mask, must be so colored due to an agouti genotype. Such dogs can not be e/e at MC1R because an Em allele is required for the production of a melanistic mask. This further confirms that dogs in breeds where mask is part of the standard such as Bullmastiffs and Boxers, the reddish coat colors are due to the agouti alleles and not an e/e genotype at MC1R.

    Since the mask is inherited as a dominant trait, a dog could be heterozygous or homozygous for mask. The extent of the mask or depth of color do not seem to be affected by the number of copies of Em. Melanin pigment can be black, grey or brown and therefore the term "melanistic" mask includes all these types of masks.

    Some dogs with melanistic mask have premature greying of the muzzle but this does not seem to be correlated with whether they are homozygous or heterozygous for mask. The Great Dane, Bridget is only 22 months old in this photo.

    Since eumelanin occurs in black, brown and blue/grey, the melanistic mask can occur in any of these colors. Manner, on the right, is a fawn Chinese Shar-Pei with a brown mask.

    Only some French Bulldogs have melanistic masks of black hairs but this breed has considerable black pigmented skin on the muzzle which sometimes shows through the pale hairs, as illustrated by Sadie at the left whose genotype is e/e at MC1R. Note that Sadie has no black hairs but still has some black skin and black nose leather and pads.

    Jester, a Kerry Blue Terrier, has the genotype EM/E. He is about 8 months old in the photo on the left and about 3 in the photo on the right. His coat has changed from black to blue but his black mask, called "points" in this breed, did not change. This change to "blue" is called "clearing" in Kerry Blue Terriers.

    Masks are present on all Bull Mastiffs and Pugs. Masks would not be visible on black, brown or born blue dogs, however, only fawn, cream, or red ones.

    All Boxers have masks too but sometimes they are born completely or almost white. Such white Boxers carry the allele for mask, even if they don't show it. Riley and Thibault both have a trace of a black mask though.

    Some coat patterns such as Harlequin, merle and Irish spotting can make it impossible to see the mask. Pirate is a Harlequin Great Dane that carries the EM allele, but his mask doesn't show. Likewise dogs that are black or brown or blue do not show their mask against their similar body color.

    Breeds in which the DNA change causing Melanistic Mask has been detected

    In some breeds all dogs have a mask. This is called "fixed" in genetic lingo since the trait is fixed and never varies. "Variable" in the table below means some individuals in the breed have a mask and others do not.

    Breed Name Fixed or Variable
    Afghan Hound Variable
    Akita Variable
    Boxer Fixed
    Bullmastiff Fixed
    Cardigan Welsh Corgi Variable
    French Bulldog Variable
    German Shepherd Variable
    Great Dane Variable
    Greyhound Variable
    Kerry Blue Terrier Variable
    Pug Fixed
    Rhodesian Ridgeback Variable
    Scottish Deerhound Fixed
    Shar-Pei Variable
    Tervuren Fixed
    Toy Poodle Variable

  • Schmutz, S. M., T. G. Berryere, N. M. Ellinwood, J. A. Kerns, G. S. Barsh. 2003. MC1R studies in dogs with melanistic mask or brindle patterns. Journal of Heredity 94: 69-73. (Originally presented by Schmutz, S. M. May 16, 2002. Coat color inheritance in dogs. Advances in Canine and Feline Genomics. St. Louis, MO.)

  • The figure below shows the MC1R peptides in the dog with the mutations discussed above that occur within the gene shown (Schmutz, unpublished).

    Yet another MC1R alelle was discovered by Rob Loechel in English Cocker Spaniels. This mutation causes a "zobel sable" coat color.

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