Effect of SAD Light Treatment on dSERT Gene Expression, Motor Function, and Aggression in Drosophila melanogaster

Abstract

Seasonal Affective Disorder (SAD) is a major depressive disorder that manifests during fall and winter months. Previous studies have indicated that SAD may be linked to a downregulation of the neurotransmitter serotonin, which also regulates aggressive behavior. The goal of this project was to determine whether treatment with light therapy increases serotonin levels, and if treatment during development can affect adult behavior. For our study we chose to measure the effect of light therapy on expression of the dSERT (Drosophila serotonin transporter) gene and male aggression in Drosophila melanogaster. To accomplish this we randomly sorted larvae into either a control group that was kept in the dark for three days, or an experimental group that was treated daily with light therapy for 20 minutes. RNA extraction and Reverse Transcription quantitative Polymerase Chain Reaction (RT-qPCR) were used to measure dSERT expression in Drosophila larvae, and a behavioral assay was used to measure aggression in adult males. We predicted that the experimental group would display upregulation of the dSERT gene and less aggressive behavior than the control group. Collectively, these findings would suggest that exposure to light therapy increases serotonin production during development, thereby resulting in a decrease in aggressive behaviors in adults.