In addition to FASPS, four of the five individuals showed signs of depression, Fu said.
"[The depression] is most likely caused by the same thing," she said. "As we probe deeper into how this mutation causes sleep problems, it very likely will also give insight to how the mutation will cause depression."
Hunt, the NIH sleep disorders researcher, said the potential link between FASPS and depression is intriguing. But he adds that the current research is unclear on which comes first.
"People who have this syndrome are viewed by society as aberrations," he said. "The depression may be secondary to society's reaction to their sleep pattern."
Of Mice, Flies, and Humans
In subsequent experiments, Fu and colleagues inserted the mutated FASPS gene into fruit flies and mice. They found that it caused a similar clock shift in the mice but had the opposite effect on the flies. The flies became more like night owls.
The results indicate that, even though the clocks of mammals and insects have similar genetic components, "there are some fundamental differences in the mechanisms that regulate the clock," Fu said.
Further study of the differences between flies and mammals may reveal how circadian rhythms are established and maintained, according to the study authors.
Hunt said this research is important because "it provides additional insight and additional opportunity to understand the molecular mechanisms of circadian clock regulation."
Ultimately, Fu said she and her colleagues hope their research will lead to a better understanding of how the human clock ticks and controls behavior.
Such knowledge may lead to therapeutic treatments for everything from sleep disorders like FASPS and jetlag to potentially related ailments such as depression and cancer.
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