Optic target regulation of NADPH-diaphorase by larval retinal axons in Drosophila.

Development of the visual system in Drosophila requires the establishment of precise retinotopic connections between photoreceptors and their synaptic targets in the central nervous system. Nitric oxide (NO) has been implicated as a candidate signal involved in the establishment of retinal projection patterns. In this study the expression of NADPH-diaphorase in the lamina of Drosophila, and by implication nitric oxide synthase (NOS), was investigated in larvae with varying degrees of retinal innervation. NADPH-diaphorase expression was seen to increase in the lamina and eye disk following retinal neuronal death in eye specific pro-apoptotic larvae (pGMR-hid) compared to wild type larvae, and was lower in the lamina in absent or reduced retinal innervation mutants (eyes absent and sine oculis). Retinal innervation is seen to regulate the expression of NADPH-diaphorase expression in target structures.