Identification and Characterization of Two Novel Sleep Promoting Neurons Located in the Ventral Nerve Cord of Drosophila Melanogaster

Sleep is a phenomenon that is ubiquitous in the animal kingdom and can be found in nearly every evolutionary niche that has come about. Humans cannot live without it, and it is required for optimal physical and mental health. Despite its importance, we have yet to discover the reason or reasons for which animals require sleep, making the study of sleep a rich vein of inquiry. Sleep is regulated by the circadian clock and the sleep homeostat, which primarily reside in the brain and communicate via complex neurocircuitry. Though difficult to study in mammalian systems, Drosophila melanogaster, the fruit fly, has become a tractable model for this kind of study. With its high degree of homology to mammals and unparalleled genetic toolbox, it is an invaluable asset in studying the neurobiological and molecular aspects of many behaviors, including sleep. In the Drosophila sleep field, the 23E10-GAL4 driver is the most widely used tool to modulate sleep. 23E10-GAL4 expresses in the dorsal Fan-Shaped Body (dFB), a brain region whose associated neurons are believed to be a major sleep regulating center. However, because the dFB contains a group of 31 neurons and the 23E10-GAL4 driver expresses in many other neurons of the fly's nervous system, it is difficult to link individual neurons to observed sleep phenotypes when manipulating 23E10-GAL4 neurons. To identify which neurons in the 23E10-GAL4 driver modulate sleep, we undertook a Split-GAL4 approach to genetically dissect out the individual neurons expressed in the 23E10-GAL4 driver. We screened 22 Split-GAL4 lines based on 23E10-GAL4 and identified a pair of neurons in the ventral nerve cord, the equivalent of the fly's spinal cord, that modulate sleep when manipulated. Through immunohistochemical experiments and RNAi knockdown, we found that these cells use acetylcholine as their primary neurotransmitter. Furthermore, we found that the number of dFB neurons contained in a Split-GAL4 line did not indicate whether it promoted sleep. Therefore, this dissertation has both identified a novel pair of sleep regulating neurons in the fly and has also raised new questions concerning past and future studies done using the 23E10-GAL4 driver in Drosophila sleep research.

Name thesis:degree_name

Ph.D. (Doctor of Philosophy)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Molecular Biology and Biochemistry (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2023

Author dc:creator

• Jones, Joseph David

Advisor dc:contributor.advisor

• Dissel, Stephane

Handle dc:identifier.uri

https://hdl.handle.net/10355/96464

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/96464