An arctic wolf in the Zoo de Servion VD: The arctic wolf owes its white coat color to a genetic variant that it inherited from a long-extinct relative. (Archive image)
The coat color of dogs and wolves is genetically determined. In fact, over 300 genes are known to date that can play a role in the development of coat color, as the genetics professor Tosso Leeb from the University of Bern explained to the Keystone-SDA news agency.
The international research team led by Danika Bannasch, professor at the University of California Davis (USA) and visiting researcher at the University of Bern, concentrated in the study on a specific gene that codes for the signal protein called agouti.
This protein causes pigment-forming cells to produce only the yellowish pheomelanin, which is responsible for light colors from white to yellow to red. If, on the other hand, there is no agouti signal protein, the black pigment eumelanin is formed.
There are two so-called promoters on this gene: One promoter ensures that the animals have a light-colored coat on their belly. The other promoter lets the hair grow banded – alternating black and yellow, which leads to a grayish coat color, which is characteristic of the gray European wolf, for example.
The combination and different characteristics of these promoters result in a total of five different color patterns in dogs and wolves, as the researchers were able to show on the basis of 77 genomes: between a very light coat, such as that found in arctic wolves, to a very black coat with only a little light on the stomach like the Bernese Mountain Dog. In between there are, for example, dogs and wolves with weak bands and a light belly, like the wolves in the Himalayas.
By comparing the gene sequences with other animal species from the canine family, they found that the overactive variant of the hair cycle-specific promoter in light-colored dogs and wolves is more similar to the sequences of distant relatives such as the golden jackal or the coyote, than with the gray European wolf. “This can only be explained by the fact that this variant must have originated at least two million years ago in a now extinct relative of wolves,” said Leeb in a communication from the University of Bern.
The researchers assume that these gene variants helped wolves in the past cold ages to camouflage themselves better in snow and ice – just as is still the case with polar and Himalayan wolves today.