Glaucoma is a neurodegenerative disease that affects ~64 million people, with a predicted rise to of 111 million people world-wide by 2040. During glaucoma, retinal ganglion cell (RGC) axons are damaged and this causes the RGCs to die, ultimately resulting in the irreversible loss of visual function. Currently, there are no FDA-approved drugs or therapies to protect RGCs from death in glaucoma. This is a major barrier in the field and one that must be addressed given the predicted rise in glaucoma incidence over the next 20 years. Neuroprotective therapies are critically needed to maintain the health of the RGC even while its axons might be damaged from glaucoma. Here, we utilize the zebrafish as an innovative discovery platform through which we can identify genes and pathways that convey neuroprotection to RGCs after acute axonal injury. Zebrafish are an ideal model for neuroprotective gene discovery because almost all RGCs survive even when the optic nerve is completely transected, indicating that endogenous neuroprotective strategies are present that preserve RGC integrity while RGC axons are repaired and regenerated. Most of the field has focused on identifying pathways critical for axonal regeneration and we know almost nothing about the neuroprotective pathways that maintain the RGCs after axonal damage. Experiments in this proposal leverage this unique biology of zebrafish RGCs to serve as an in vivo platform for identification of novel neuroprotective strategies. We hypothesize that both endogenous (RGC) and exogenous (non-RGC) pathways mediate neuroprotection. For the latter, modulation of macrophage/microglia-derived inflammatory responses has recently emerged as one such potential exogenous pathway affecting cell survival after damage in a number of neuronal contexts, including glaucoma. The molecular underpinnings of this dependence are largely unknown. We hypothesize that factors released from macrophages and microglia after optic nerve injury limit pathological inflammation and stimulate pro-survival pathways in RGCs. Here, we test these two hypotheses to identify novel neuroprotective strategies that protect RGCs from injury-induced death. The results of this study will be significant to the field by providing a list of in vivo-relevant neuroprotective factors that can be screened for efficacy in mammalian systems, potentially serving as the foundation for the development of novel neuroprotective strategies that are effective in keeping RGCs alive in the earliest stages of glaucoma.