COAT COLOR IN THE TOLLER: Breed history and current genetics.
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Here is an example of a sable pup with light eyes and brown nose pigment. These pups also usually fade to a nice rich red.
AGOUTI LOCUS: Most all Tollers are homozygous for the sable agouti allele called ay. The Bannasch Laboratory tested 16 Tollers and found that they were all homozygous for the agouti allele sable. Anecdote suggests that there are some tan-point (at)Tollers (think Doberman markings), so this recessive allele may well exist in this breed. Tan-point puppies are the result of a mating with two tanpoint carriers. In Tollers, in order to see the tan points the dogs must also have a specific allele at MC1R- more in the next section!
The agouti series works by modifying the amount of black versus yellow hair in the coat. One extreme is an all black dog and the other extreme is an all yellow dog. In between these two extremes are the sable color, black and tan and the normal allele which gives a strong banded pattern like you see in wolves.
a^y = Dominant allele that restricts dark pigment distribution; produces fawn/sable.
a^w = agouti "wild-type" allele: gives wolfgrey coloration. Also called a^g.
a^t = tan point allele: gives bicolored animal; dark body with tan points.
Red (mahogany dark red to bright red to even pale yellow) animals with any black hairs in their coats (even if only as puppies!) are a^y genetic sables. This "color"--which varies wildly in shade given its optics--has many names in dog breeds, but is traditionally called sable from the black overlay on a red coat. If the animal is a <bb> recessive "brown" dog, this is going to be less obvious than with one with black hairs, but shading of any kind along the spine especially
suggest the dog is a a^y sable. Sables tend to lighten as they age: many pups look "muddy" at birth but are a bright clear color by adulthood typically, so bright reds that are genetic sables could easily be confused as adults with the
"clear red" described next. The distinction between a sable and a clear red Toller would only be noticed at a young age.
EXTENSION LOCUS: Clear red animals, or "gun dog reds," are recessive for an allele at MC1R called e. These animals are unable to express dark (eumelanin) pigment in their hair coat, but can still show it in their skin (including eyes, as well as lips & noses). So, clear red Tollers can have black (or brown) noses and eye rims, but never appear shaded even though they are all also technically "sables" in the sense they are a^y agouti homozygotes. The genetic term for this is called epistasis and basically it means that the action of one gene can mask the action of the other. If no dark pigment is produced then you can't see if it is distributed into banded hair or tan points. It takes at least a single dominant <E> for any of the A locus genes to express. So Tollers that are shaded reds, puppies that had masking or sabling when young, these dogs have at least one dominant <E> gene at the extension locus. Labrador yellows, Irish Setters, and all Goldens are typically <ee> "recessive" reds. As Tollers apparently have both reds present in the breed, and both reds can interact with the "3rd" dog "red"--which is actually the B recessive brown described below-it's important to recognize all these reds do not come from exactly the same genetics, even if they look a lot alike. So, with so many "reds", the situation in this breed is likely subtle as to variation and requires a careful eye.
The MC1R gene has two known alleles that are now well defined:
- E = allows for self colored dog; i.e. the actions of alleles of the Agouti locus can be seen.
- e = restricts pigment to red/yellow (no dark pigment can form).
The shade of red/yellow here is in large part a result of variation unrelated to the MC1R gene's main action, as <ee> clear red dogs, like aY homozygous shaded red dogs can come in a variety of shades. MC1R red dogs are typically born paler so their puppy coat is lighter than their ultimate adult color. This is a distinction to the shaded or agouti red, where the puppy is darker than the adult, because the coat typically “clears” as that dog matures. Also, it's commonly observed that the paler shades of clear"red" (which can be very pale yellow or even cream) cannot produce the darkest shades of clear red, i.e. dark red or dark golden puppies do not ever come from pale blond parents in Breeds like Golden Retrievers and Labradors. So assumably some other pigment gene is acting here.
Clear or “Gun-dog” Red Tollers from Pups to Adult
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Clear red pup with brown pigment ~ Clear red pup with black pigment |
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According to what we know of the history of the Toller, the initial focus in the creation of this breed was in creating a red dog, something resembling the coloring of a fox. In order to achieve this, red from a variety of different canine sources was used. This has given Tollers mutations in three different red causing genes. Since most Tollers tend to either darken or lighten toward a similar tone of red as adults, no matter which color they looked like as pups, Toller breeders generally don't distinguish between clear red or sable red when defining the colors of their pups on registration paperwork. The AKC choices for Tollers when defining the color of Toller puppies are "Red", "Golden-Red", "Fawn" and "Buff". "Red" is the default color on the paperwork, but really, genetically what differentiates a "red" from a "golden-red" from a "fawn"? Sometimes, it's nothing, just shades of a clear-red dog, but sometimes it's a sabling gene hidden in that rich red coat. There really is nothing in the registration paperwork color choices which clearly indicates whether the dog is a sable or clear red. In the adult Toller this is a subtle difference, but for those who want to know what colors they are mixing into the "paint" of their puppies there are genetic tests available that can give breeders an exact picture of the color genetics he or she is dealing with. Color genetics testing is available through companies like Healthgene and Vetgen for a reasonable price.
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