Reversing age-related epigenetic changes and characterizing microglia heterogeneity in obesity and aging

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Project Summary Neuroinflammation is a hallmark of brain aging that may contribute to declines in function and neurodegenerative diseases. As the resident macrophage of the brain, microglial are crucial to brain maintenance but have been demonstrated to take on pro-inflammatory phenotypes with aging. The proposed research will examine the role of microglia-specific epigenetic mechanisms in aging and determine the effects of obesity and aging interactions on microglia phenotypic heterogeneity. We will determine whether aberrant age-related microglia-specific epigenetic patterns can be reversed by heterochronic plasma approaches. Additionally, we will determine how microglia subpopulations differ with age and obesity at a single-cell level with special interests in lipid-droplet- accumulating microglia (LDAM). The goals of the training are to: 1) obtain a strong knowledge and foundation in animal and nutritional models of anti-aging and obesity 2) gain hands-on experience in technologies and bioinformatic skills needed for various omics approaches in specific hippocampal cells and at a single-cell level 3) apply these skills to achieve the research aims outlined in this proposal and 5) gain experience and improve oral and presentation skills, manuscript and grant writing to enable a transition to independence. In Aim 1, we hypothesize that exposure of old mice to young plasma will reverse age-related microglia-specific DNA modifications to restore ‘youthful’ epigenomic patterns. This is based on the premise that DNA modifications are key regulators of the diverse phenotypes required for the fulfillment of microglia functions which are disrupted in aging. We will determine whether the administration of plasma from young into old mice can reverse age-related microglial-specific hippocampal epigenetic and transcriptomic changes in Cx3cr1:NuTRAP mice using whole genome oxidative bisulfite sequencing (WGoxBS) and RNA sequencing, respectively. These studies will identify specific genomic sites amenable to the rejuvenating interventions and serve as targets for future epigenome editing studies. In Aim 2, we will determine how the interaction of obesity and aging affect microglia heterogeneity. We hypothesize that high-fat diet leads to expansion of pathological LDAM resulting in impaired microglial function, which can be reversed by late-life calorie restriction. We will use single-cell transcriptomic analysis, bulk transcriptomics and microglia functional assays (phagocytic uptake and cytokine/chemokine analysis) to determine changes in microglia subpopulations in dietary-induced obese mice with age. In addition, we will determine whether starting calorie restriction at 12 months in dietary-induced obese mice can mitigate the effects of obesity on microglia heterogeneity. This will help identify mechanistic insights into microglia heterogeneity, LDAM and obesity-associated neuroinflammation. In total, the training goals and objectives will provide the needed skills and expertise to pursue a research career focused on developing anti-aging interventions.