PROJECT SUMMARY Microglia, the resident neuroimmune cells of the CNS, play important developmental roles. During embryonic development we showed that retinal microglia target a subset of viable newborn retinal ganglion cells (RGCs) for phagocytic elimination through a process that requires complement signaling. The embryonic retina is a simple system to address how microglia target non-apoptotic cells for phagocytosis, with important implications for the role of microglia in cell loss during injury and disease. To understand the mechanisms of retinal cell elimination, the first aim will address the role of complement expression and stress pathways in RGCs. The second aim will test specific microglial recognition pathways required for phagocytic retinal cell elimination, including RGCs and astrocytes. This study will shed light on how microglia influence developmental remodeling in the retina, and may ultimately inform our understanding of how microglia participate in retinal disease processes resulting in loss of vision.