Testing Summary
The e2 Locus (Australian Cattle Dog Type) coat color test reliably determines if a dog has one of the following genotypes at the e2 locus:
| N/N | This dog does not carry a copy of e2 and has a genotype of N/N which does not result in cream coat color in the Australian Cattle Dog. This dog will pass one copy of N to 100% of its offspring. Interpretation: No cream |
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| e2/N | This dog carries one copy of e2 which does not result in cream coat color in the Australian Cattle Dog unless the dog is also a Carrier of one copy of the e variant. However, the dog’s coat color is also dependent on the dog’s genotypes at the K, A, and B genes among others. This dog will pass one copy of e2 to 50% of its offspring and one copy of N to 50% of its offspring. Interpretation: No cream (carries cream) |
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| e2/e2 | This dog carries two copies of e2 which results in a cream coat color in Australian Cattle Dogs. However, the dog’s coat color is also dependent on the dog’s genotypes at the K, A, and B genes among others. This dog will pass one copy of e2 to 100% of its offspring. Interpretation: Cream |
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Detailed Summary
The two major pigments that impact canine coat color are eumelanin (black pigment) and phaeomelanin (yellow/red pigment). These pigments are produced within specialized cells called melanocytes located in the canine epidermis and hair follicles. The MC1R gene, also known as the extension E Locus controls the production of eumelanin in the melanocytes. The dominant form of the MC1R gene (E) allows for normal production of eumelanin in the melanocytes. However, DNA variants in the MC1R gene can prevent production of eumelanin in the melanocytes leaving only the production of phaeomelanin. Because the e and e2 variants of the E Locus are recessive, two copies of one of these variants or one copy of each variant must be present to express the cream coat color in the Australian Cattle Dog. A dog that has two copies of the dominant E Allele (E/E) will not have a cream coat and will not be capable of passing on a cream coat allele to its offspring. A dog that has one copy of E and one copy of e (E/e) or e2 (E/e2) will not have a cream coat but will pass on the cream gene e or e2 to 50% of its offspring and the black coat color gene E to 50% of its offspring. A dog that has two copies of e (e/e), two copies of e2 (e2/e2), or one copy of each variant (e/e2) will have a cream coat and will pass one copy of the e or e2 variant (depending on the dog’s specific genotype) to 100% of its offspring.
Testing Tips
The e2 Locus (Australian Cattle Dog Type) coat color test evaluates the MC1R gene to determine the e2 locus genotype for the dog. Cream coat color in the Australian Cattle Dog is inherited in an Autosomal Recessive fashion. Thus, two copies of this Mutation (or one copy of e2 and one copy of the e variant – also known as the e1 variant) are associated with cream coat color in this breed. Thus, testing for both the E Locus e and e2 alleles may be necessary to determine if a dog is a Carrier of this cream coat color. However, the dog’s coat color is also dependent on the dog’s genotypes at the K, A, and B genes among others. Normal results do not exclude inherited mutations not tested in these or other genes that may also contribute to coat colors and traits in dogs. Reliable genetic testing is important for determining breeding practices.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
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Dürig N, Letko A, Lepori V, Hadji Rasouliha S, Loechel R, Kehl A, Hytönen MK, Lohi H, Mauri N, Dietrich J, Wiedmer M, Drögemüller M, Jagannathan V, Schmutz SM, Leeb T. Two MC1R loss-of-function alleles in cream-coloured Australian Cattle Dogs and white Huskies. Anim Genet. 2018 Aug;49(4):284-290.
[PubMed: 29932470]
