Genetic mutations determine feather colour in pigeons

Scientists have identified mutations in three key genes that determine feather colour in domestic rock pigeons.
The same genes control pigmentation of human skin and can be responsible for melanoma and albinism, researchers said.
"In humans, mutations of these genes often are considered 'bad' because they can cause albinism or make cells more susceptible to UV (ultraviolet sunlight) damage and melanoma because the protective pigment is absent or low," said Eric Domyan, a biology postdoctoral fellow at the University of Utah and first author of the study.
Various forms of a gene named Tyrp1 make pigeons either blue-black (the grayish colour of common city pigeons), red or brown, researchers said.

Mutations of a second gene, named Sox10, makes pigeons red no matter what the first gene does. And different forms of a third gene, named Slc45a2, make the pigeons' colours either intense or washed out, researchers said.
The scientists discovered how pigeons' feather colour is determined by different versions of these three genes - known as variants or alleles - and by what are called "epistatic" interactions, in which one gene obscures the effects of other genes.

"Both Tyrp1 and Sox10 are potential targets for treatment of melanoma. Mutations in Slc45a2 in humans can lead to changes in skin colour, including albinism (lack of skin colour)," said Michael Shapiro, senior author of the study.

Different versions of the three major pigeon-colour genes affect the relative proportions of major forms of the melanin pigment- eumelanin and pheomelanin- and their distribution within cells.
Eumelanin provides black and brown pigmentation, while pheomelanin provides red and yellow pigmentation of feathers. Interplay among the three major genes is complex, resulting in diverse colouration of pigeons.
"Mutations in one gene determine whether mutations in a second gene have an effect on an organism," Domyan said.
In other words, one gene can mask the effects of another in relation to pigeon colour.
The three pigment genes don't control how the colours are distributed in patterns on pigeons' bodies, such as white patches of feathers on some breeds. The genetics of colour patterns remains to be determined, researchers said.

The scientists showed that feather colours in 82 breeds of pigeons could be explained by various combinations of the three genes and their different versions.
Shapiro and co-workers found that versions of the Tyrp1 gene were responsible for determining three basic pigeon colours: blue-black, ash-red, and brown.
Blue-black colour of pigeons is considered "normal," because neither Tyrp1 nor the other two major colour genes contain mutations in these pigeons. City pigeons typically are this colour.
The study was published in the journal Current Biology.