Function and connectivity of Relaxin3 neurons in the zebrafish visual system: from single-cell physiology to behavior. – FunCoRelax

In Bilaterians, the transfer of information between hemispheres is crucial for brain function, particularly for binocular vision. Commissural neurons, connecting both sides of the brain, are essential in this process. Although their existence is well-documented, the complexity of their neuronal composition and their function remains far from fully understood. Although their existence and neuronal identity is well-documented, the function of brain commissures at the neuronal circuit level, as well as their development, remains a significant challenge. This project aims at deciphering their function at the neuronal circuit level and their development in the optic tectum of the zebrafish larva, an organism ideal for exploring both hemispheres simultaneously due to its size and transparency. I have recently identified a population of bilateral neurons with contralateral projections expressing the neuropeptide Relaxin3, to be anatomically close but distinct from a subtype of commissural neurons whose function in binocular integration was discovered by my host team. While the role of Relaxin3 in arousal, stress, and cognition is well established, its function in vision-mediated behaviors remains unknown and unexplored to date. This project aims to decrypt the cellular physiology of Relaxin3 neurons, their development, synaptic connectivity, and assess their roles in processing external stimuli and resulting behaviors. The project is structured around 3 axes: (i) Determining their functions during visual processing by combining calcium imaging, optogenetic manipulation, and behavioral analysis (ii) Mapping their anatomical and functional connectivity using electrophysiological, connectomics, and voltage imaging techniques (iii) Identifying the role of the neuropeptide Relaxin3 in the function of the zebrafish visual system.