The ability of animals to interpret sensory information and produce complex behaviours relies on the perfect functioning of their brains. These consist of highly diverse neuron and glial populations.
How these cells are generated and assemble into complex functional neural circuits during development remains poorly understood.
Our group uses the visual system of Drosophila as a genetic model to address these issues. Photoreceptor cells (R-cells, R1-R8) extend axons from the retina into the optic lobe, which consists of four main areas, lamina, medulla, lobula and lobula plate. R-cell axons and target neurons are closely associated with glia and form hard-wired specific connections within reiterated columnar and layered synaptic units. We are particularly interested in the cell-type specific molecular programmes and mutual interactions of afferent axons, glia and target neurons that regulate the stepwise formation of this circuit.
Specifically, we study the development of selected neuron and glial subtypes in higher visual information processing areas. Furthermore, to understand how laminated circuits form, we focus on the targeting steps of the color-sensitive R8 photoreceptors to their temporary and final layers, as well as layer-specific axonal and dendritic branching of target neuron subtypes. By analysing the mechanisms underlying normal brain development we hope at long term to advance our understanding of neurological disorders linked to developmental connectivity defects.
Figure 1: Schematic representation of the adult Drosophila visual system. R1-R6 photoreceptor axons terminate in the lamina, while R8 and R7 axons stop in two neuropil layers in the medulla. Target neuron subtypes display characteristic columnar and layered axonal and dendritic arborizations. Neurons are found in close association with glia.
Figure 2: Confocal image of an adult fly visual system. Photoreceptor neurons (R1-R8, red) extend axons into the lamina and medulla. Labeling of a subset of target neurons with GFP (green) reveals the regular organization of their processes into columns and layers.