Researchers led by Vanderbilt's Roger Cone, Ph.D., have discovered a new member of a gene family that has powerful influences on pigmentation and the regulation of body weight.
The gene is the third member of the agouti family. Two agouti genes have been identified previously in humans. One helps determine skin and hair color, and the other may play an important role in obesity and diabetes.
The new gene, called agrp2, has been found exclusively in bony fish, including zebrafish, trout and salmon. The protein it encodes enables fish to change color dramatically to match their surroundings, the researchers report this week in the early edition of theProceedings of the National Academy of Sciences (PNAS).
The first agouti gene, which produces the striped "agouti" pattern in many mammals, was discovered in 1993. The same year, Cone and his colleagues at Oregon Health Sciences University in Portland reported the discovery of the gene that encoded the melanocortin-1 receptor, a key player in the pigmentation story.
They demonstrated that the agouti protein prevented the melanocortin-1 receptor in melanocytes (pigment cells) in the skin from switching on production of black-brown pigment, and instead shifted the pigment to yellow-red hues.
The second agouti gene encodes agouti-related protein (AgRP), which blocks a melanocortin receptor in the brain. It prevents the melanocortin-4 receptor from inhibiting food intake, and thus stimulates eating.
