Gene regulation affects sex-based sleep differences in flies
Science & Tech Editor
A visiting researcher spoke about his research on the sleeping pattern of fruit flies Tuesday at The University.
David Garbe, Ph.D., a senior research investigator from the University of Pennsylvania, made a presentation entitled “Investigating sexually dimorphic patterns of behavior in Drosophila (lessons from sleeping flies).” In it, Garbe defined circadian rhythms, summarized his most recent research findings and provided examples of future research if he were to become an assistant professor of animal physiology at The University.
Many organisms with more advanced sensory perception exhibit bodily changes on a daily basis known as circadian rhythms. Garbe explained the necessary requirements for a cyclic activity to be considered a circadian rhythm.
“Circadian rhythms,” Garbe said during the presentation, “are over a period of 24 hours, entrained to the environment, persist in the absence of environmental cues and exist across a broad range of temperatures.”
The cycles essentially help an organism adapt to and anticipate changing environmental circumstances to it them survive on both a daily and long-term basis.
These changes, specifically those involved with the fruit fly, Drosophila, interested Garbe and his team at Sehgal Laboratory at Penn, where they explored how sleep cycles of Drosophila differed between males and females. Garbe’s team approached the phenomenon of sexual dimorphism in regards to sleeping patterns in Drosophila from both a molecular biological and organismal perspective.
From an organismal perspective, Garbe and his fellow researchers expanded upon the already-established sexually dimorphic behavioral characteristics of fruit flies. Previous work established that male fruit flies display aggressive behavior when placed in a chamber together, while a male and female pairing in a chamber undergo courtship behaviors. Using infrared beams to detect wakefulness, Garbe’s team determined that in addition to the sex-dependent behaviors, fruit flies exhibit differential sleeping patterns corresponding with sex; males sleep more during the daytime than females do. Upon documenting this dimorphism, Garbe sought to determine a genetic basis for the behavioral difference.
From a molecular biology standpoint, Garbe’s team investigated the protein PERIOD (PER), which can act as a transcription factor for the clock gene period (per). Per modulates sleeping patterns in flies. The team hypothesized that diurnal circadian phosphorylation of PER rhythmically affected the rate of per transcription.
Garbe described phosphorylation as “a post-translational modification that changes the function of a protein.”
In other words, the addition of a phosphate group to a protein changes its shape, thereby changing its function. The team identified 35 serine/threonine residues phosphorylated throughout the day.
Garbe recognized that further work needed to be done as he said, “We are interested in uncovering the protein involved in phosphorylation of (PER).” In Garbe’s recent paper in PLoS Genetics, he and his team identified the proteins that dephosphorylate PER, while those that phosphorylate it remain unknown.
Garbe then brought his results back to an organismal standpoint when he revealed further findings: mated female flies sleep less during the day than virgin female flies. Garbe’s team turned to a protein transmitted via semen during copulation known as the sex peptide (SP). Previously known behavioral effects of SP include increased male rejection from females and increased egg laying. Garbe’s team looked into SP as a potential means to modulate mated female fly sleep patterns, but it determined that the post-mating neuronal circuit that modulates male rejection and egg laying is distinct from that of the sleep pattern.
Garbe hopes to continue research into the sexual dimorphism of flies to fully characterize the reasons behind the differences in sleeping patterns.
March 6, 2015