Investigating the Ontogenesis of Serotonergic and Dopaminergic Neurons in the Drosophila Embryo

Serotonin and dopamine are monoaminergic neurotransmitters that modulate complex behaviours such as learning and memory, sleep and feeding. They are synthesized through enzymatic reactions from the amino acids tryptophan and tyrosine, respectively. Drosophila melanogaster is a widely used model organism for studying neurogenetics and developmental biology, yet the genesis of serotonergic and dopaminergic neurons during embryonic development remains poorly understood. Previous studies have examined the expression of serotonin, dopamine, and related genes at the last embryonic stage and during larval development. However, the expression of key genes regulating the expression or the function of these two neurotransmitters has not been studied in detail in early development. In this report, I investigate the presence of serotonin and dopamine during embryonic development and examine the expression of key genes encoding enzymes, transporters and receptors related to the two neurotransmitters. Using a novel in-situ hybridisation technique, hybridisation chain reaction (HCR), I obtained new insights on the timing of expression and the spatial distribution of the transcripts. Subsequent immunofluorescence experiments were aimed at documenting translation, which not necessarily starts in parallel with transcription or at all. Unfortunately, these experiments were only partially successful and the same applies for the direct immune detection of serotonin and dopamine. In summary, this project has progressed the description of the ontogeny of the serotonergic and dopaminergic pathways during early development in Drosophila laying the foundation for future investigations