Afghan Hound Coat Colors and DNA Tests
a brief explanation of how currently available DNA tests can help predict some coat colors
This webpage is part of a series on Dog Coat Color Genetics. It was first mounted before April, 2006 and was last updated on June 22, 2010 by Sheila Schmutz
News - Domino Genetics Unravelled!
By mid-October the original set of dogs and the official Saluki Coat Color Study was completed. The research phase to address the gene/s causing grizzle was completed in spring 2010. This research lead to the study of domino in Afghans as well. The manuscript describing this will be published in Journal of Heredity in Fall, 2010 but is available as "online early". A free PDF copy of the manuscript is available for download. Note that the Afghan photos and Table showing the Afghans in this study are also availabe under Supplementary Data (see gray bar at the right of the Journal of Heredity page).
HealthGene will be offering testing for this mutation soon.
The E Locus
All colors are acceptable in Afghan Hounds in most countries, but nevertheless people have preferences. DNA testing for the E alleles in Afghan Hounds allows breeders to better predict the colors of pups from particular matings. All 3 typical E alleles (EM, E, e) have been shown to exist in Afghans. However, like Salukis, they have a fourth allele EG. The dominance hierarchy is: EM > EG > E > e.
Afghans may be red from two different genetic mechanisms. These are virtually indistinguishable when one looks at red dogs. One genotype which causes red is a y at the agouti locus, as demonstrated by Claudia at the right. Because ay is dominant the other alleles at this locus, one copy is enough to cause this type of red that is called fawn in many breeds. Such red dogs are E/-, ay/- or EM/-, ay/- depending of whether or not they have a mask.
The second genotype which causes a red coat color in Afghans is e/e at the MC1R gene. This may be more rare but we have not tested enough dogs to be sure of this yet. Dogs which are "e/e" can not be brindle or domino, even though they may carry the alleles for these patterns at other genes. They also never have a mask. All of those patterns include black and black pigment can not be produced in dogs that are "e/e" because the mutation in the MC1R gene prevents any eumelanin pigment in hair. However the nose and pads and eye rims of such dogs can still be black because pigmentation at these locations is affected by the B locus or TYRP1 gene.
|Photo by Stephanie Hunt-Crowley|
|Photo by Barbara Lessmeister||
A black mask only occurs in Afghans that carry at least one EM allele. It is typical for such dogs to have black ear fringe also. Although a mask is not visible on black or blue Afghans but only on fawn, cream and brindle Afghans, it can occur in dogs of all these colors. Kaschmir, at the left, is cream because he is a dilute red but he has a striking black mask. EM is the "top dominant" allele in this series.
The A Locus
The A locus is the Agouti Signal Peptide gene (ASIP). There are four common alleles at this locus with a dominance hierarchy of: ay > aw > at > a. It would appear that only ay and at exist in Afghans.
Dogs which have the genotype at/at in the presence of other suitable alleles (at least one E or EM and ky/ky), are black-and-tan. Tai and his cloned puppy Snuppy who has recently been verified as a true clone, are this coloration. Since they have a black mask they have at least one EM allele.
Afghans with the at/at could also be blue-and-tan, black-and-cream, blue-and-cream, or have brindle undersides if the appropriate alleles are present at other genes to alter this pattern.
Domino Afghans have the genotype at/at and ky/ky but they must also have at least one EG allele and no EM allele. Beck is a domino Afghan with an EG/e genotype.
Nola is a domino Afghan with brindle. Note the brindle stripes on her face. Nola is homozygous EG/EG.
All Afghans with a solid colored body have at least one ay allele. Such dogs could be black, blue, brindle, fawn, or cream.
Afghan coats often change color from birth to maturity, so early DNA testing may help to predict their adult color. The DNA tests we have verified in Afghan Hounds thus far are available from Healthgene Laboratory (Canada).
The K Locus
Although Little (1957) suggested that ebr was another allele in this series that caused brindle, recent DNA studies prove that brindle is caused by an allele of the K locus, Kbr.
|Photo by Stephanie Hunt-Crowley||
Dogs with a single KB allele are black unless they are e/e. Twinkle is an example of a black Afghan. Twinkle's genotype is EME but one can not see her black mask against her black coat.
Dogs that are Kbr/Kbr or Kbr/ky are brindle (unless they are e/e). The dominance heirarchy is KB > Kbr > ky at this locus. Precious is an example of a full body brindle Afghan pup that is diluted to grey and cream stripes, instead of black and fawn stripes.
The gene is beta-defensin 103. DNA tests are now available to determine if a dog is KB/KB or ky/ky. The brindle mutation is complex and a DNA test is not available to determine which black dogs might be carrying brindle.
The D Locus
The D locus has recently been shown to be the melanophilin gene (MLPH). There appears to be more than one d allele. Dogs with a d/d genotype are "born blue". We have only tested a single Afghan that was born blue so far and it did not have the common mutation found in Weimaraners, Great Danes, and Grehounds. Until the other mutations are identified, DNA testing can not be used to detect "born blue" in Afghans.
A DNA study is currently underway to determine the gene that causes black to become blue and red to become cream over time. Many Afghans lighten with age due to a phenomenon called "progressive graying". Little suggests that this is caused by the G locus. The gene causing this has not been identified so far.
Cream colored Afghans with no mask, such as Lulu, right can be E/E, E/e, or e/e. The hints of reddish color seen on her ears suggests that her underlying color is red but because her genotype is E/e, we know it is ay type red and not e/e type red.
|Photo by Stephanie Hunt-Crowley|
Sponenberg and Rothschild describe a gene they name I for Intense that dilutes only phaeomelanin. Diluted phaeomelanin colors are sometimes called cream, buff, apricot, lemon, etc. Such a gene, undoubtedly exists. However this gene has not yet been identified or even mapped in the dog.
Kaschmir, the cream Afghan Hound with a black mask at the top of the page, is a striking example of a dog that only dilutes phaeomelanin and not eumelanin. His mask is still very black, even though his body is almost white.
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