What controls the coat colour patterns in dogs?

Researchers have successfully uncovered the secret behind the inheritance of coat colour patterns in dogs. A genetic variant responsible for a very light coat in dogs and wolves originated more than two million years ago in a now extinct relative of the modern wolf (Nature Ecology and Evolution).

Wolves and dogs can make two different types of pigment, black (eumelanin) and yellow (pheomelanin). Regulated production of these two pigments at the right time and at the right place on the body gives rise to very different coat colour patterns.

The so-called agouti signalling protein represents the body’s main switch for the production of yellow pheomelanin. If the agouti signalling protein is present, the pigment-producing cells will synthesise yellow pheomelanin. If not, black eumelanin will be formed.

According to the University of Bern release, dogs have a ventral promoter, which is responsible for the production of agouti signalling protein at the belly. An additional hair cycle-specific promoter mediates the production of agouti signalling protein during specific stages of hair growth and enables the formation of banded hair.

They also discovered two variants of the ventral promoter. While one of the variants conveys the production of normal amounts of agouti signalling protein, the other causes increased production of the protein. They also identified three different variants of the hair cycle-specific promoter. Thus dogs have a total of five different combinations, which cause different coat colour patterns.

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