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Olfaction Receptors Found in Fruit Fly

Lead researcher: Leslie Vosshall

Researchers in Dr. Richard Axel’s laboratory have discovered several genes that code for odor receptors in the fruit fly, Drosophila melanogaster. Similar genes in humans were discovered in Dr. Axel’s lab almost a decade ago. The discovery of odor receptor genes in the fruit fly provides new tools for extensive laboratory experimentation that could help neurobiologists better understand olfaction in mammals. It also may help scientists find valuable weapons to control insects that transmit human diseases and damage crops.

It took postdoc Dr. Leslie Vosshall five years to find the genes, but she finally succeeded where more than a dozen other laboratories had failed. In 1994, Dr. Vosshall and Dr. Hubert Amrein, then also a postdoc in Dr. Axel’s lab, identified 250 genes expressed only in the fruit fly antennae, that animal’s olfaction organ. After technicians sequenced those genes, Drs. Vosshall and Amrein found one gene that resembled odor receptors found in other animals. But they needed to find several more similar genes before they could claim to have found the members of the odor receptor family.

That second phase proved "enormously frustrating," says Dr. Vosshall, as several different molecular techniques failed to uncover any more odor receptor genes. But by 1998, scientists around the world had sequenced about 10 percent of the fruit fly genome. Dr. Vosshall felt confident that somewhere in that portion of the publicly available fruit fly genome would be additional members of the odor receptor family of genes.

"We needed to find a genome person with a great computer to crunch through the genome database," says Dr. Vosshall. She turned to postdoc Dr. Pavel Morozov and associate research scientists Dr. Andrey Rzhetsky at the Columbia Genome Center who generated a list of 2,500 potential odor receptor genes. Dr. Vosshall painstakingly whittled that list down to six genes similar to the one she and Dr. Amrein had found. Dr. Vosshall and her colleagues published their results in the March 5, 1999, issue of Cell.

Results so far indicate that each olfactory neuron carries one kind of receptor, as do mammals. A single odorant molecule can probably bind to several receptors, and fruit flies sense a specific odor by detecting which odor receptors have been activated.

Dr. Vosshall estimates that the fruit fly has about 100 to 200 odor receptor genes. She expects that all of the odor receptor genes will be discovered soon after the entire fruit fly genome is sequenced, within the next year or so. Having a complete set of those genes for such a popular laboratory animal will enable researchers to forge ahead in understanding how flies, humans, and other species smell.

Indeed, according to an article in the journal Science, researchers are already using the newly found receptors to look for similar ones in insects that damage agricultural crops in hopes of finding chemicals that can interfere with their ability to detect odors, on which they rely to find mates and food.

The research was supported by the Howard Hughes Medical Institute, the National Institute of Mental Health, and the National Institute of Neurological Disorders and Stroke.

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