In a four-year, round-the-clock search, researchers screened 9,000 mutated fruit flies, many of them supplied by Ganetsky's lab, and found one line of them that slept one-third the amount of normal flies. Put through a series of tests, the short-sleeping flies, named minisleep (mns), were found to perform normally and did not appear to be impaired by sleep deprivation. The mns flies, however, did have shorter life spans.
Following the testing, the researchers noticed shaking in the flies' legs as the insects recovered from anesthesia. The observation led the team to focus on the Shaker gene, which produces this effect. Nevertheless, Shaker's main job in flies-and in its equivalent in humans--is to control the excitability of cell membranes.
Genetic analysis of the mns flies, conducted by Daniel Bushey, a post-doctoral fellow working with the Tononi team, revealed that their Shaker genes contained a single amino-acid mutation. Because of the mutation, a functional ion channel could not be formed on the cell membrane and potassium therefore could not flow through it.
When the researchers first tested flies with the Shaker gene, they found that some of them with other mutations were normal sleepers. But these flies became short sleepers when the researchers removed genetic modifiers from their genome.
"This told us that genetic forces push hard against this phenotype to make it ineffective," Cirelli says. "Being a short sleeper is probably not a good thing. We know that the mns mutation affects mortality, but we're not sure how."
In earlier studies, Tononi's team discovered that fruit flies do, in fact, sleep.
"The more behaviors we look at, in terms of sleep, the more we find that sleep in fruit flies is very, very similar to sleep in mammals," Cirelli says.
Like humans, fruit flies generally are quiet and immobile for between six and 12
Source:University of Wisconsin-Madison