E Locus - E^g (Grizzle, Afghan Hound Type)

Testing Summary

The E^g Locus (Grizzle) coat color test reliably determines if a dog has one of the following genotypes at the E^g locus:

Detailed Summary

The E^g variant of the MC1R gene produces a characteristic coat color pattern consisting of a black pigmented widow's peak on the head of the dog with other black tipped hairs on the back of the dog similar to some sable or saddle tan colorations. The grizzle coat color pattern has only been observed in the saluki, Afghan hound (referred to as "domino" in this breed) and the borzoi (referred to as "sable" in this breed). Although the E^g variant of the MC1R gene is dominant to E and e, it is recessive to E^m (melanistic mask). Therefore, the grizzle coat color pattern is only expressed if the dog does not have an E^m variant (i.e., does not have a melanistic mask) and is also k^y/k^y for the K Locus and a^t/a^t for the A locus.

Testing Tips

The grizzle coat color pattern in some breeds of dog is inherited in an Autosomal Dominant manner meaning that dogs only need to inherit one copy of E^g to have the characteristic grizzle patterning. In addition, grizzle patterning is only produced if the dog has a k^y/k^y genotype at the K Locus and an a^t/a^t genotype at the A locus. However, E^m is dominant to E^g so grizzle dogs cannot carry any E^m alleles. Dogs with an E^g/E^g genotype will have a grizzle coat color if the above conditions are met and will pass on E^g to 100% of its offspring. Dogs with only one copy of E^g will pass on E^g to 50% of their offspring and will produce puppies with grizzle coat color patterns approximately 50% of the time depending on the genotypes at the E^m, K, and A loci of both partner dogs. Non-grizzle dogs can be bred to other non-grizzle dogs or dogs with disqualifying E^m, K, and A genotypes to produce non-grizzle dogs.

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

• Dreger DL, Schmutz SM. A new mutation in MC1R explains a coat color phenotype in 2 "old" breeds: Saluki and Afghan hound. J Here. 2010 Sep-Oct; 101(5):644-49. [PubMed: 20525767]
• Everts RE, Rothuizen J, van Oost BA. Identification of a premature stop codon in the melanocyte-stimulating hormone receptor gene (MC1R) in Labrador and Golden retrievers with yellow coat color. Animal Genetics. 2000 Jun; 31(3):194-99. [PubMed: 10895310]