Every month, I answer pet owner questions on the Ask the Vet podcast, or when I’m invited on Dr. Frank Adams’ Pets and Your Health program on SiriusXM’s Doctor Radio. It’s not often that a caller stumps me, but a few weeks ago someone asked about the poodle fading gene—a term I had not heard of before. Apparently, poodle owners have noticed a progressively lightening or “fading” in poodles’ coats over time, and suspect a genetic connection. After a lot of reading, this blogpost will “shed” some light on the poodle fading gene.
Genetics of Coat Color
Dog fur comes in a range of colors—white, yellow, red, brown, black—and patterns such as solid, spotted, brindle or merle. Their fur can be long, medium, short; straight or curly. Given all these possibilities, it’s no surprise that the genetics determining a dog’s coat and its color are complex. Different gene combinations can even result in the same coat color and pattern.
One gene, MC1R (melanocortin 1 receptor), plays a central role in determining coat color in dogs and other species.
MC1R and Pigment Balance
Coat color is determined by a balance of two pigments in the fur:
Eumelanin, which causes black or brown coloration
Pheomelanin, which causes yellow or red coloration
MC1R controls the production of these two pigments by controlling the enzymes that produce the pigments. Simplistically, more eumelanin produces a black coat, and more pheomelanin results in a red coat.
A variation in MC1R called R301C has been identified in DNA samples from dogs living 10,000 years ago. This variant is still present in some dogs today including a variety of Spitzes, scent hounds such as the beagle and some foxhound breeds. Chihuahuas, Chinese Crested dogs and Alaskan breeds such as the husky can also have this variant gene. R301C is a partially recessive red variant. Depending on the interaction with other genes, it can create coat shades that range from cream to tan to fawn.
MC1R is such a critical gene in coat color determination that the canine R301C variant of MC1R is present in other species, including light coated alpacas and Arabian camels. A similar variant is present in chestnut horses.
What About the “Poodle Fading Gene”?
Despite an extensive hunt, I could not find a scientific description of a specific “poodle fading gene.” The internet has a good deal of confusing and contradictory information and little science. Some say the gene is dominant. This means if either parent passes the gene to their pup, the pup’s coat color will lighten over time. Others say the gene is recessive. Greying and silvering genes are yet another potential cause of poodle fading syndrome.
Human Influence on Canine Coat Color
The R301C mutation resulting in the red coat of some dogs appeared early in dog domestication. Its perpetuation in the canine population may be a result of human preference. Humans may have selected dogs with red coats because they were more easily seen or because the coat colors were associated with a desirable behavioral trait such as herding or tameness. And of course, novelty may have played a role since even cavemen might have wanted something different than what everyone else has.
The Importance of MCR1 Beyond Fur Color
MCR1 is important in making your dog the fluffer that you know and love, but it has other, more significant health related roles. MCR1 is responsible for eumelanin synthesis, which protects the skin from UV radiation damage. MCR1 signals cells to repair DNA damage. In humans, the type of MCR1 gene you have predicts your risk for melanoma, a type of skin cancer. Similarly, in Standard Poodles, a variant of MCR1 protects against squamous cell carcinoma of the toe.
The Takeaway
While this blogpost doesn’t answer the question I set out to answer, it at least makes me feel better that part of the reason I didn’t know the answer to the poodle fading gene question is there is currently not an answer! The genetics of coat color are intricate, and ongoing research may one day reveal the mechanism behind fading in poodles. Until then, we can only admire the mystery behind every shade of fluff.