GENETIC TESTING FOR COAT COLOR AND LENGTH IN THE SHIBA INU
This Japanese import puppy, living in France, tested “aw/at” at UC Davis.
Typical markings seen on an ay/at sesame.
“THE BLACK PIGMENT IN DOGS IS CREATED BY THE MELANOCORTIN 1 RECEPTOR (MC1R) WHICH IN ITS
DOMINANT FORM, E , ALLOWS FOR BLACK HAIRS ON A DOG, AT LEAST AT SOME POINT IN THEIR LIVES, EVEN IF IT’S JUST ONE BLACK WHISKER. ALL SHIBAS HAVE THIS EXCEPT FOR THE CREAM.”
and Akitas. Dogs carrying the ee have no black hairs anywhere on their bodies, ever, but have black pigment elsewhere as seen in Irish Setters and Golden Retrievers. The intensity of pigment can range from Irish Setter red to Shiba cream. Theories have been put forth, especially by Clarence C. Little (1957) in his book, The Inheritance of Coat Color in Dogs , regard- ing the genes that may influence the intensity of red pigment, but there are no tests available to determine this—yet. It is interesting to note, though, that Shar-Peis have both the dark red ee pigment as well as the cream variation with no intermediate shades like the Golden Retriever or Chow. Shibas do not appear to have the dark red ee , as they would have to be born red with not even one black hair, and only the creams do that. The ee red or cream color in dogs is not to be confused with the liver-pigmented red found in Dobermans and Vizslas. That gene does not appear to occur in Shibas, and always has brown points (nose, lips, etc.). All Shibas have at least one black hair, except creams. The other gene series expressed in the Shiba is the Agouti caused by the Agouti Signaling Protein (ASIP). The ASIP interacts with MCIR to create all the colors that we see in the breed, from red through black & tan. Although there are four known variants of the Agouti gene, recent tests by UC Davis Laboratories have shown only three in the Shiba. The most dominant is for the sable (Shiba people call it red) which is Ay . Shibas not carrying the black & tan recessive are Ay/Ay. It is common knowledge that black & tan is recessive to red, and it is designated at/at . Red and sesame dogs carrying the black & tan recessive are most frequently Ay/at , but the recent development of a definitive test for the black & tan recessive has allowed geneticists to determine if a dog has the wild, aw , gene by default. There is no definitive test for the aw gene and it is determined by process of elimination.
into a breeding is the ratio that comes out with approximately one in four expressing the recessive gene when both parents are carriers. If both parents are long-coats, ll , all offspring will be long-coated. It is easy to see how the long-coat gene can be passed down for generations and never be expressed; especially when many more offspring than any combination would ever produce is necessary to get the balanced ratios. For additional information on how this works, type “Punnett Square” into a search engine. Space does not permit a discussion of all the tests available that influence canine coat color, so only those that affect the Shiba will be noted. A basic discussion of all the coat colors for which there are tests may be seen on the University of California at Davis’ website. Actually, Shiba coat color is fairly simple compared to the vast array of possibilities for the Afghan Hound or Great Dane. Mam- mals really only have two coat color pigments, black and red/yel- low. Everything in the Shiba, from red to sesame to black & tan to cream, is a variation on a theme. There are now tests available for what causes white socks or “pinto” markings in the dog, and these may even be a by-product of domestication, but that is a whole other article. The black pigment in dogs is created by the Melanocortin 1 Receptor (MC1R) which in its dominant form, E , allows for black hairs on a dog, at least at some point in their lives, even if it’s just one black whisker. All Shibas have this except for the cream. In its recessive form, e , all black pigment is restricted. If a Shiba has two copies of the gene, ee , it becomes cream. Recent test samples on Shibas that are cream or cream producers show that Shibas that do not carry the recessive for cream are EE , those that are colored and have produced cream are Ee , and cream is ee . These findings are concurrent with a similar expression of the ee gene in Shar-Peis
SHOWSIGHT MAGAZINE, MAY 2022 | 233
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