The primary role of the nervous system is to perceive conditions in our surroundings and elicit the appropriate behavioral response. This is controlled by complex neural circuits that are interconnected through long cable-like structures called axons. One important group of axons arises from serotonin-producing brain cells, which integrate with circuits throughout the nervous system to modulate behaviors such as mood, sleep, appetite, and cognition. Ultimately, these behavioral outputs are determined by the precise growth and wiring of axons. Recent work by the PI and others in the field has shown that serotonin-producing brain cells use serotonin itself to help shape its axons during early stages of development. This research will utilize cutting-edge genetic tools available in fruit flies, Drosophila melanogaster, to understand how this molecular mechanism works inside the cells, how it shapes circuits in the brain, and how it impacts behavioral output. The fruit fly nervous system is built with the same basic components, which assemble and direct neural activities as they do in the human nervous system. The knowledge gained will therefore provide insight into how abnormal serotonin exposure during development can lead to behavioral disorders in humans. These studies will provide students with multidisciplinary research experiences in genetics, cellular biology, and neuroscience through paid research positions. By reducing financial barriers to undergraduate research at an