By Cat Holmes
University of Georgia
A University of Georgia researcher has discovered a chicken
gene which, when manipulated, makes birds fatter or and
thinner. However, it works only in female chickens.
“The same gene exists in males, but it doesn’t do the same
thing,” said Sammy Aggrey, the quantitative and molecular
geneticist in the UGA poultry science department who found the
growth hormone receptor gene. “Some genes work in one gender
and not in another.”
Identifying the growth hormone receptor gene in chickens and
understanding how it works could have important implications
for human research.
Obesity is growing at epidemic proportions in the United
States. According to the Centers for Disease Control and
Prevention, more than 44 million Americans are now obese, an
increase of 74 percent since 1991.
Humans and chickens are enough alike that Aggrey’s discovery
and other genetic research on chickens may lead scientists to
similar findings in humans.
“One of the beauties of using chickens is that the research can
be done quickly,” Aggrey said. “Then biomedical researchers can
use it right away in their work with humans. When we find genes
in chickens that act in a certain way, we expect to find the
same types of genes in humans.”
Aggrey said it’s wrong, though, to call the growth hormone
receptor gene a “fat gene” or a “female fat gene.”
“Many people think that if you pinpoint a gene like this, you
can simply manipulate the gene to gain or lose weight. It’s not
that simple,” Aggrey said. “Behavior and the environment, non-
genetic factors like nutrition and activity level, play large
roles.”
How can a gene express itself in females but not in males?
The reasons are complex, Aggrey said. But they boil down to
this: While both sexes have most genes in common, genes located
on the sex chromosome differ. Often, as in humans and chickens,
one gender has a single copy of that gene and the other has a
double copy of it. This causes the gene to take different
actions in each sex.
Aggrey is also involved in a larger obesity-related study to
identify and map all the genes involved in growth and fatness
in broiler chickens.
For this project, he works with researchers at the universities
of Delaware and Maryland and the National Institute for
Agricultural Research in France. The latter is an agency much
like the U.S. Department of Agriculture.
“It’s a huge project to identify and characterize that many
genes,” he said. “Last year we discovered spot 14, which is one
gene for fatness.” Spot 14 has since been shown to be connected
to obesity in humans and mice.
(Cat Holmes is a news editor with the University of Georgia
College of Agricultural and Environmental Sciences.)
