Gene Mutations In Rock Pigeon Pigmentation Have Implications For Human Medical Research

Brett Smith for redOrbit.com – Your Universe Online

A team of American researchers has discovered mutations in three genes that determine feather color in domestic rock pigeons, according to a new study in Current Biology. The same genes direct the pigmentation of human skin – meaning the findings may have implications for medical research.

“Mutations in these genes can be responsible for skin diseases and conditions such as melanoma and albinism,” said study author Michael Shapiro, associate professor of biology at the University of Utah.

“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 study author Eric Domyan, a biology postdoctoral fellow at the University of Utah. “In pigeons, mutations of these same genes cause different feather colors, and to pigeon hobbyists that is a very good thing.”

The study team learned that coding and regulatory distinctions in the interactions among the genes Tyrp1, Sox10 and Slc45a2 affect multiple color phenotypes, or appearances, in pigeons. In one instance, scientists learned that a “reddish” mutation in Tyrp1 arose just once and was spread all through the species by selective mating. Different forms of Tyrp1 make pigeons blue-gray, red or brown.

Variations of Sox10 make pigeons red, regardless of what form Tyrp1 takes, the researchers found. Also, Slc45a2 makes the pigeons’ colors either very strong or look washed out.

“Our work provides new insights about how mutations in these genes affect their functions and how the genes work together,” Shapiro said. “Many traits in animals, including susceptibility to diseases such as cancer, are controlled by more than one gene. To understand how these genes work together to produce a trait, we often have to move beyond studies of humans. It’s difficult to study interactions among the genes in people.”

“Both Tyrp1 and Sox10 are potential targets for treatment of melanoma,” he added. “Mutations in Slc45a2 in humans can lead to changes in skin color, including albinism (lack of skin color).”

Different versions of the three main pigeon-color genes affect the general proportions of significant forms of the melanin pigments – eumelanin and pheomelanin – and their circulation within cells. Eumelanin supplies black and brown pigmentation, while pheomelanin supplies red and yellow coloring of feathers. Interaction among the three major genes is complex, the researchers said.

“Mutations in one gene determine whether mutations in a second gene have an effect on an organism,” Domyan said. In this case, one pigmentation gene can hide the effects of another.

The study team indicated that feather colors in 82 breeds of pigeons might be explained by various reactions among the three genes and their different versions.

“Color is one of the most important traits to breeders − it makes a pretty pigeon,” Shapiro said.

Breeders’ manipulations have led to great color diversity in pigeons over the years, providing scientists with ideal specimens for studying pigmentation genetics.

“Darwin realized that blue-black was the ancestral pigeon color, and that the various domestic rock pigeon breeds represented a single species,” Shapiro said, noting that when Darwin crossed different colors of pigeons, blue-black pigeons regularly appeared among the progeny.