My main projects in the Barnea Lab revolve around the establishment of transsynaptic tracing tools in Drosophila. When I joined, the laboratory was working on trans-Tango, an anterograde transsynaptic tracing tool where a ligand-receptor interaction at synapses results in gene expression in the postsynaptic partners of a group of starting neurons. I was lucky enough to be part of this exciting project.
Once this project was published, my focus shifted to developing different iterations of trans-Tango. Although trans-Tango proved to be very useful in circuit tracing in the adult nervous system of fruit flies, it had background noise in the Drosophila larval nervous system. Therefore, my immediate aim was to tackle this problem by generating different configurations of trans-Tango and assaying them for their performance in larvae. After having established a version that works well, trans-Tango MkII, my colleagues and I combined circuit tracing with neuronal loss-of-function, gain-of-function, and epistasis experiments to reveal part of the neural circuitry that mediates a robust larval behavior, light avoidance.
In addition, trans-Tango was designed to work only in the anterograde direction, yet there was also need in the Drosophila neuroscience community for a reliable and user-friendly tracing tool to determine the inputs of a circuit. For this, I started to tweak trans-Tango such that it would work in the retrograde direction. This project, that we had initially thought would be trivial, proved to be more challenging than we expected. However, after years of trying and failing, I, together with a group that I led in the Barnea Lab, generated retro-Tango for retrograde circuit tracing in Drosophila. Now, we are collaborating with other groups to establish trans-Tango (available as a preprint) and retro-Tango for circuit tracing in Zebrafish.
Currently, I am collaborating with other members of the Barnea Lab to establish the use of two separate trans-Tango systems in the same animal. In the first configuration, the two trans-Tango pathways are in series, enabling differential identification of monosynaptic and disynaptic partners of a group of neurons. We, hence, named this configuration ds-Tango for disynaptic Tango. Using this method in the olfactory system of Drosophila, we identified node neurons that are postsynaptic to all three sexually dimorphic olfactory circuits that mediate the courtship behavior. Right now, we are characterizing these neurons via activation and inhibition experiments. Excitingly, we, very recently, discovered that the thermogenetic inhibition of these neurons leads to exuberant male-to-male courtship which rarely happens in the wild. This result indicates that these node neurons are important for identifying the sex of the conspecifics. In future work, I intend to use the circuit tracing systems we developed to identify the circuit that mediates proper courtship behavior downstream of these neurons.
For the second configuration, we intend to use two separate trans-Tango pathways in parallel and we named this version p-Tango for parallel Tango. Using p-Tango, one will be able to identify shared and distinct postsynaptic neurons in two different neural circuits within the same animal. Thus, p-Tango will allow for circuit intersection studies, currently an unmet technical challenge. Although p-Tango is similar, in idea, to ds-Tango, it requires more components. The entry and the exit into trans-Tango and its derivatives are both established via binary gene expression systems. For ds-Tango the exit of the first pathway is the entry of the second pathway, hence, three binary expression systems are sufficient. For p-Tango, however, since the two trans-Tango pathways are in parallel, there is need for a fourth binary system to be used either as an exit or as an entry for the second pathway. Currently, we are working on finding this fourth binary system. Once this is achieved, we will use p-Tango to identify neurons that are common to different sensory modalities that play a role in the courtship behavior.
