Survival of glia in optic lamina is maintained by EGFR signal provided by photoreceptors in adult Drosophila visual system. Yuan-Ming Lee^1,2, Y. Henry Sun^1,2. 1) N415, Inst Molecular Biology, Taipei, Taiwan; 2) Institute of Genomic Science, National Yang-Ming University, Taipei, Taiwan.

   In the Drosophila visual system, the photoreceptor neurons send their axons into the optic lobe of the brain. The R1-6 neurons terminate in the lamina and make synaptic contacts with lamina neurons. In the lamina, the axons are surrounded by multiple types of glia. We found that when the endocytosis in glia is blocked in adult flies, the lamina glia will degenerate due to lysosome accumulation. The degeneration is progressive and irreversible, and accompanied by impaired phototransduction and motor activity. EGFR signaling in the glia is required and sufficient to maintain their survival. The survival signal is the EGFR ligands provided by the photoreceptors. These results suggest that the photoreceptors actively maintain the survival of glia in the adult visual system. Whereas many studies have shown that neurons and their target cells mutually maintain each others survival, our findings show that neurons actively maintain the microenvironment integrity of their target field.