Afferent growth cone interactions control synaptic specificity in the Drosophila visual system.

In the Drosophila compound eye, photoreceptors (R cells) that respond to light from the same point in space are distributed across the retina and connect to the same target neurons. This complex connectivity pattern reconstructs visual space in the first optic ganglion, the lamina. We have used mutations that delete specific R cell subtypes or alter their retinal organization to define the cellular mechanisms that generate this pattern. R cell axons are programmed to search for targets within a local region in the lamina but their selection of appropriate postsynaptic targets requires specific interactions among R cell growth cones. The orientation of the projections is controlled both by the spatial arrangement of R cells in the retina and by cues in the target.