Project Summary Aging is a progressive process in all cells that leads to tissue dysfunction and is a major cause of degenerative changes. Aging cells show characteristic patterns of epigenetic changes that are often cell-type and tissue- specific. The development of methylation-based clocks has harnessed this phenomenon and is successfully used to predict the biological age of cells, tissues, and organisms across species. However, the functional implications of these epigenetic changes are not well understood. Furthermore, bulk analyses of aging cells limit the identification of subtle, unique, cell-type specific changes. Therefore, investigating cellular aging mechanisms with single cell resolution is essential for teasing out these cell-type specific changes. Most blinding diseases are a result of age-related retinal degeneration, for which there are currently no treatments. It is essential to understand the molecular mechanisms that regulate retinal aging to identify targets and develop therapeutics to slow or prevent the onset of these degenerative diseases. I propose to use approaches that have previously been applied to studying retinal development and regeneration to conduct a comprehensive analysis of normal retinal aging with single cell resolution to identify gene regulatory networks that control cellular aging in the retina. I will determine how acute injury influences the rate of retinal aging, and test potential retina specific aging targets to slow the aging process. I will manipulate expression of transcription factors whose activity is altered by natural aging, injury, and/or rejuvenation, and determine whether this can regulate cellular age. Completion of this work will create accurate cell type-specific molecular aging clocks for all major retinal cell types, identify gene networks and targets that control cellular aging, and determine if modulation of these networks can be used to rejuvenate cells. The datasets created in this work will not only enhance the study of retinal aging, but cellular aging throughout the central nervous system in general.