A mutation in a dog gene opens new research into the defensin protein

Ruby, a poodle, donates DNA for research with cheek swab.

Researchers who were trying to find the mutated gene that controls coat color in dogs now report that they found the gene and have also discovered that it has an unexpected additional role. The gene also sends a signal to a member of a protein family that is responsible for defending the body against infection. The proteins are called defensins, because their job is to defend the body.

Dr. Greg Barsh

“So instead of just finding the gene we were looking for, we found something more important,” explained Dr. Greg Barsh. “We found that a protein family no longer has one job as we thought, and new studies can tell us what else defensins are involved in besides fighting microbes and determining the color of a dogs coat.”

In most mammals, coat color is determined by two genes that decide if the mammal will have either a dark or light coat. But dogs are different -- they have a third gene that makes the decision.

Now that the genome sequence, or library of all of the genes, for dogs is available, genetic researchers started looking for the precise gene responsible for coat color. They knew it was within a small section of the dog DNA they called the K locus. The researchers compared the small sections of the DNA in Boxers and Great Danes to find the one gene. Then they found the gene in the DNA of hundreds of dogs they studied.

Since defensins are now involved in immunity and coat color, researchers will investigate what other roles defensins may be involved in.

About the Researcher:

Greg Barsh is a medical doctor who is also a researcher. Early in his career, he became interested in improving human health and moved into biomedical research. “My motivation for studying dogs is to learn as much as possible about the signaling pathways that the pigmentary system plays in human development and disease,” he said. A particular interest in that system is to finding the cause of early onset childhood obesity.

This study appears in the 19 October issue of the journal Science.

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