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Fruit flies offer scientists insight into human diseases

WASHINGTON — Most people think of fruit flies as annoying little pests zipping around bananas or grapes on the kitchen counter. But to biologists, they are diamonds on the wing.

These miniature aerial acrobats have been a basic tool of biomedical research for nearly a century. They've unlocked many secrets of animal and human genetics, development and evolution, and they continue to provide valuable insights into cancer, heart disease, diabetes, obesity and neurological disorders.

Fruit fly researchers have won two Nobel Prizes, first in 1933 and again in 1995.

After all that time and toil, you might think there's little new to be discovered. But the field is undergoing a revival, attracting thousands of researchers who ground out almost 16,000 scientific papers in the last five years.

The National Institutes of Health is investing more than $180 million a year in their work, according to Laurie Tompkins, the program director at the NIH's Division of Genetics and Developmental Biology in Bethesda, Md.

``Fruit flies are major contributors to understanding what goes wrong in cells that cause disease,'' said Lynn Cooley, a geneticist at Yale University in New Haven, Conn. About three-quarters of human genes associated with disease have counterparts in fruit flies, she said.

``We are in a renaissance period,'' said Dr. Susan Celniker, a fruit fly expert at the Lawrence Berkeley National Laboratory in Berkeley, Calif. ``We now have fly models for all types of human diseases.''

The revival is due to recent advances in genetics that allow scientists to decipher the DNA that makes up human, animal and plant genomes. Eleven new fly species' genomes were decoded last year.

Fly researchers used to study genes composed of hundreds or thousands of molecules. Now they can work with great precision at the level of individual molecules.

The formal name of this scientific pet is Drosophila melanogaster — Greek for ``black-bellied dew-lover." Most workers in the field simply call themselves ``fly people.'' They go ``fly-mining'' for new data, which they store in an online ``FlyBase.'' They hoard thousands of live flies in ``stock centers'' in Bloomington, Ind., and Tucson, Ariz.

Researchers have discovered surprising aspects about the lives of these little creatures. Fruit flies love sweets and suffer from obesity and eating disorders. They have immune systems against viral diseases. They can detect motion 10 times faster than the human eye can, which makes them maddeningly hard to capture.

Some researchers study what they call the ``emotional behavior'' of flies.

David Anderson, a biologist at the California Institute of Technology in Pasadena, has shown experimentally that the tiny creatures can sense fear. Ralph Greenspan, a neurobiologist at the Neurosciences Institute in San Diego, Calif., has bred fighting flies.

"My lab is studying the genetics of aggression in flies,'' Cooley said. `` If you put two males in a container with a female, they fight each other with their legs and wings. It looks like a boxing match.''

Fruit flies have courtship rituals. A male fly woos a female by "singing'' a song created with his wings, while a female waits demurely for her suitor to approach.

Fly researchers claim credit for many discoveries connected to human disease.

For example, Tian Xu, a geneticist at the Yale School of Medicine, studies how cancerous cells in flies ``metastasize," or spread to other cells, similar to the way they do in human malignant tumors.

``Our fly model has distinct advantages for studying the basic biology underlying tumor progression and metastasis,'' Xu wrote on his Web site.

A fly gene called ``Twist'' has a corresponding gene that causes deformities in human embryos when it's not working right.

Fruit flies are more distant genetically from humans than are mice, biologists' other favorite experimental animal. But fly researchers say their insects have advantages over laboratory mice. Many basic genes were discovered first in flies and then studied in mice and humans.

``The huge disadvantage of mouse systems is it costs so much to house and feed them,'' Cooley said. "It's much more difficult to do experiments. It takes a lot longer for generations to develop. We can move lot faster and cheaper in flies.''

Asked why the tiny fruit fly is worth so much money and effort after nearly a century of study, Cooley replied: ``So much in biology still a vast unknown. It may seem surprising, but just scratch little below the surface of what we know, and you realize how much we don't know. ''

ON THE WEB

More information on http://www.flybase.orgfruit flies. Click on News, click on White Papers.

Read a href=&qhttp://www.mcclatchydc.com/144">more stories by Robert S. Boyd/a>.

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