Identification and characterization of sleep-wake circuits in Drosophila larvae

Julci looking into a microscope.




Assistant Professor of Psychiatry and Neuroscience

Project Summary

Sleep is required for normal physiological function in all organisms. In particular, sleep is hypothesized to have a critical role in brain development. However, systems have not effectively studied sleep during the earliest periods of neural development.

The fruit fly, Drosophila melanogaster, exhibits sleep behaviors. Behavioral characteristics of sleep are shared between mammals and flies. While this model is a powerful tool, neurogenesis is almost complete in the adult brain. The Kayser Lab has expanded upon classic fly work to devise methods of studying fly larvae. We have determined that larvae indeed meet the criteria for sleep.

The goal of my project is to map and characterize specific neurons in 2nd instar larvae that play a role in sleep and wake. These experiments are a part of a larger plan to understand how neural control of sleep/wake changes throughout the lifespan.

In this screen, the GAL4-UAS system was used to drive expression of TrpA1 in GAL4-specific neurons. TrpA1 encodes for a thermosensitive cation channel which opens and depolarizes the neuron when the temperature is above 30ºC. Using infrared imaging and pixel analysis, the average number of bouts, average bout length, average activity, and total sleep time was calculated and compared between groups of GAL4-specific larvae. GAL4 lines were selected in which larvae displayed deviations in total sleep, but not in average activity. After selection, more experiments were performed to see if the sleep phenotype exists only with increased temperature, and to check that there is no permanent effect. To visualize the neurons where these GAL4s are expressed, I imaged 2nd instar larval brains using confocal microscopy.

My contribution to this project has been a wonderful opportunity to further my research from last summer and expand upon my knowledge of Drosophila genetics and systems neuroscience. This work prepared me for my internship this summer at HHMI Janelia Research Campus, where I was able to widen my skillset by researching associative learning in the larval brain. I attended workshops and guest speakers, met famous scientists and ambitious PhD students, learned about cutting-edge techniques, gained familiarity with the different fields of neuroscience, and developed a better sense of the area that I would like to work in. By designing posters and presenting at journal club, I refined skills that are necessary for a future career in research. Equipped with new knowledge and experience, I am excited to devise new experiments and accelerate my success on this project.