SYNAPTIC PARTNER CHOICE DURING DEVELOPMENT OF THE DROSOPHILA VISUAL SYSTEM

Neuronal partner choice during circuit assembly is a complex process where neurons in close proximity exhibit highly specific yet divergent connectivity. To achieve this pattern, several processes must be controlled both in time and space, throughout development. We are interested in the molecular and cellular mechanisms underlying the formation of neural circuits that process specific visual cues for navigation. We use the skylight polarization pathway as a model system to investigate the targets downstream of photoreceptors in the dorsal rim area (DRA) during development of the Drosophilavisual system. DRA photoreceptors manifest modality-specific connectivity as they avoid contacts with synaptic targets of neighboring non-DRA (color sensitive) photoreceptors despite displaying a high degree of promiscuity thereby enabling imprecise connectivity.
We aim to understand the developmental dynamics of R7-DRA and R8-DRA photoreceptor axons during selective targeting towards their respective postsynaptic partners, two distinct distal medulla neuron types, known as Dm-DRA1 and Dm-DRA2. We hypothesize that the development of a stereotypical DRA circuitry relies on spatiotemporal separation of potential partners, as well as probabilistic filopodial exploration, resulting in a modality-specific synaptogenic encounters.
We use live imaging of brain cultures to study cellular encounters and filopodial dynamics of pre- and postsynaptic targets, throughout development, both in wild type and specific perturbation experiments to manipulate synaptogenic encounters. We also use connectomic data to quantify variability of synaptic connectivity, both in the DRA and non-DRA columns. In summary, we aim to understand the importance and cost of imprecise parameters during the development of modality-specific circuitry.