University of Iowa Biological Sciences Professor Daniel F. Eberl and his colleagues at Duke University have uncovered genetic defects leading to deafness in fruit flies that may shed light on deafness in humans. Their research paper, "Myosin VIIA Defects, which Underlie the Usher 1B Syndrome in Humans, Lead to Deafness in Drosophila," is scheduled for publication in the May 10 issue of the journal Current Biology.
Eberl says their recent work -- showing that loss of function in the Myosin VIIA gene leads to complete deafness in fruit flies -- has brought scientists one step closer to understanding how such mutations result in inner-ear abnormalities and deafness in humans.
"Myosin VIIA was one of the first human hereditary deafness genes to be identified. But it is not clear exactly how this molecule works in the human ear," he says.
Previous evidence suggested that fruit flies and humans rely on the same genes to develop their auditory organs, which in the fruit fly is in the antenna. Eberl's research shows that at least one molecular component specialized for hearing function, myosin VIIA, is conserved in these ears.
In looking for clues to inherited deafness in humans, Eberl begins with the "love song" of the fruit fly. Although they may seem an odd choice, the fruit fly and its love song are very effective tools for learning about the molecular and cellular mechanisms involved in hearing in insects and animals, including humans, says Eberl, who is trying to identify the genes responsible for hearing in fruit flies.
Whether or not mutant fruit flies can hear the fruit fly love song (actually a vibrating wing) enables Eberl to evaluate the function of genes responsible for hearing. He and his graduate student, Sokol Todi, implant electrodes into the antennas of the flies, and record the voltages the receptor cells generate as the flies listen to the love song. By comparing the electrical impulses generated by the normal flies to those generated by myosin VIIA mutant flies, they showed that the myosin VIIA gene is essential for hearing in flies, as it is in humans.
Now that they know the same molecule is used, scientists will be able to design experiments to test specific mechanisms that have been hypothesized. Eberl says, "These experiments are next to impossible in humans, but quite feasible in the fruit fly."
"Understanding how this protein works and examining its functional role in hearing will provide new insights into auditory mechanisms, not only in fruit flies, but in humans, as well," he says.
The American Heart Association and the National Institutes of Health provided support for the research.
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