Blinding conditions affect millions worldwide. Retinal cell loss often precedes symptoms resulting in critical barriers for therapeutic intervention. To overcome these barriers, strategies are needed to replace retinal neurons that are lost to disease. Our long-term goal is to exploit the regenerative potential of adult retinal stem cells to replace lost retinal neurons, thereby advancing novel regenerative therapies for blinding diseases. The goal of this project is to identify genetic networks that regulate the regeneration of retinal neuron subtypes. To do so, we developed a system for studying cell-specific retinal regeneration in zebrafish, a highly regenerative species. Normally mammals, including humans, have a limited capacity for retinal regeneration. However, recent data suggests that key molecular factors can enhance retinal cell replacement in mammals. In addition, cellular and molecular mechanisms governing retinal regeneration appear to be conserved between fish and mammals. Identifying pathways which allow retinal stem cells to respond in a regenerative manner will therefore further the development of novel therapies aimed at reversing vision loss in humans. [Data from our group and others has recently shown that, in zebrafish, selective retinal neuron loss triggers a cell-specific regenerative response3, 4. In light of these findings, we hypothesize that the replacement of indivi- dual retinal neuron subtypes is associated with the activation and/or repression of specific molecular signaling pathways critical for successful regeneration of the lost cell type.] To test this hypothesis, we will perform a time-resolved analysis of gene expression changes during the loss and regeneration of [two] different retinal neuron subtypes in zebrafish: [1) rod photoreceptors and 2) bipolar interneurons (Aim 1).] We predict that genes will be regulated in temporally distinct patterns correlated to roles in 1) activating stem cell populations, 2) promoting stem cell dedifferentiation, 3) progenitor cell proliferation, and/or 4) cell-specific differentiation. Dynamic Bayesian analyses will be used to identify genes/networks likely to play central roles in determining whether disease-relevant retinal cell types are regenerated. Follow-up functional tests will be used to evaluate candidate genes regarding specific roles played in the replacement of retinal neuron subtypes (Aim 2). This research is designed to impact the fields of regenerative biology and retinal disease therapeutics. Delineation of genetic networks underlying the regeneration of specific cell types has transformative implications for both fields of study and will serve as the foundation for new therapeutic strategies aimed at reversing vision loss in humans. Our expected outcomes are: 1) generation of rich datasets revealing gene expression changes occurring as individual retinal neuron subtypes are lost and regenerated, 2) deployment of improved statistical methods for comparing datasets across cell types and over time, and 3) unique insights into the molecular regulation of adult retinal stem cells during injury-induced regenerative processes.