Using a measurement technique developed by Kernan, Walker first snipped off the tip of a fly bristle, which is about a hundredth the diameter of a human hair. He then slipped a superthin fluid-filled hollow glass pipette over the bristle.
By precisely moving the pipette, he found that he could bend the bristle. Since both the pipette and the hollow bristle were filled with liquid, Walker could measure the electrical current transmitted through the bristle from the fly neuron to which it attached.
Such studies coupled with genetic analyses revealed that several of the flies shared mutations in a particular gene, which Zuker and his colleagues called nompC, for "no mechanoreceptor potential-C." The mutant flies either lacked the transduction current or showed currents that indicated rapid adaptation to mechanical stimuli.
"We knew that these two phenotypes had to occur in the same gene, so it seemed very likely that this gene was critically involved in the transduction process," said Walker.
When the scientists isolated the nompC gene and analyzed its structure and function, they discovered that it closely resembled genes for other ion channels in flies and vertebrates, including humans.
Aarron Willingham, a graduate student in Zuker's laboratory, then explored whether a similar channel could be found in the roundworm, C. elegans, which had been used in some previous studies of mechanoreception. Willingham attached a fluorescent reporter gene to the worm homolog of the nompC gene and inserted it into the worms. The experiments indicated that the worm nompC gene was specifically expressed in the neurons that were the worm counterparts of the fly mechanosensory neurons.
"Taken together with the earlier findings that the responses of fly bristles are very similar to those of human hair cells, the disco
Contact: Jim Keeley
Howard Hughes Medical Institute