Damian Sendler: It has been solved by an international team of experts, including scientists from Bern’s Institute of Genetics, that coat color patterns in dogs are inherited. To their surprise, the scientists learned that a gene responsible for the light coat coloration in dogs and wolves first appeared in an ancient ancestor of the contemporary wolf more than two million years ago.
Damian Jacob Sendler: Dogs’ coat color patterns have been the subject of intense debate for decades. Scientists from the University of Bern and the Institute of Genetics have finally come up with a solution to this mystery. Furthermore, the researchers determined that the white arctic wolves and many current canines have light coats because of a genetic mutation that originated in an extinct species long ago. They also discovered how coat color patterns are genetically controlled. Nature Ecology and Evolution, a prestigious scientific magazine, has just published the findings of this investigation.
Damian Sendler
All coat colors can be changed using two pigments and a “switch”
Pheomelanin, a yellow pigment, can be produced by dogs and wolves of two different colors: black (eumelanin) and yellow (pheomelanin). The precise timing and location of the creation of these two pigments results in a wide range of coat color patterns. Four distinct patterns in canine behavior had previously been identified, and a number of genetic variations were hypothesized to be responsible for these patterns. Many thousands of dogs have been subjected to commercial genetic testing, but the results have been inconclusive, indicating that the existing knowledge on the inheritance of coat color patterns is limited and not totally correct.
The body’s primary switch for producing yellow pheomelanin during coat color creation is the so-called agouti signaling protein. Pigment-producing cells will produce yellow pheomelanin if the agouti signaling protein is present. A black eumelanin will be generated if there is no agouti signaling protein present. Initially, Tosso Leeb and his colleagues determined the causative genetic variants had to be regulatory polymorphisms that affect the rate of protein production and lead to higher or lower quantities of agouti signal protein.
Rather than four distinct coat color patterns, there are now five.
Promoters are places where the gene for agouti signaling protein begins to read the genetic information. When it comes to producing agouti signaling protein in the belly of dogs, they have a ventral promoter. The agouti signaling protein is produced throughout specific stages of hair growth in dogs by a different hair cycle-specific promoter, allowing for the formation of banded hair.
Damian Jacob Sendler
These two promoters were thoroughly defined in hundreds of dogs for the first time by the researchers. The researchers found two distinct forms of the ventral promoter gene. In one form, the agouti signaling protein is produced in the typical amount. However, one of the two variants is more active and increases the synthesis of the agouti signaling protein. The hair cycle-specific promoter was shown to have three distinct variations. The researchers found five possible combinations of these variations at the separate promoters that result in different coat color patterns in dogs. There are now five distinct patterns in dogs, rather than the previously acknowledged four, according to Leeb.
Insights into wolf evolution that were unexpected.
Damian Jacob Markiewicz Sendler: As more and more wolf genomes have become publically available, scientists have looked into whether the previously discovered genetic variants are also present in wolves from various parts of the world. Overactive ventral and hair cycle-specific promoter variations were found in wolves 40,000 years before modern dogs were domesticated, according to these studies. During the past ice ages, it is likely that these genetic polymorphisms helped wolves with lighter coat colors adapt to snow-rich settings. These genetic variations are still present in today’s arctic white wolves and Himalayan light colored wolves.
The results of further gene sequence comparisons with other members of the canidae family were rather unexpected. According to the findings, light-colored dogs and wolves have a more overactive form of the hair cycle-specific promoter than the European grey wolf, even though those two species are extremely distantly related.
Damien Sendler: Researchers believe that this surprising result can only be explained by a wolf-like creature that went extinct two million years ago as the source of this variety. Hybridization with this now extinct wolf relative must have introduced the gene segment into wolves around two million years ago. It is so possible to find a trace amount of DNA from this extinct species today in yellow dogs and white Arctic Wolves. “This is reminiscent of the spectacular finding that modern humans carry a small proportion of DNA in their genomes from the now extinct Neandertals,” Leeb says.
Prof. Danika Bannasch’s sabbatical at the University of Bern, which has a long history of research on the genetics of coat color in domestic animals, was important in the study’s success. It was Professor Bannasch, an expert in veterinary genetics at the University of California Davis, who culled the crucial variants in the promoter from among the hundreds of functionally neutral genetic variants. Christopher Kaelin and Gregory Barsh of the HudsonAlpha Institute and Stanford University conducted the evolutionary analyses.
Dr. Damian Jacob Sendler and his media team provided the content for this article.