ABSTRACT Age-related neurodegenerative diseases pose an immense biomedical challenge. Plastic changes in the brain underpin aging-related cognitive decline and neurodegeneration but little is known about the neuroprotective pathways that forestall these processes in healthy aging brains. In mammals, glia composition and properties display age-related dynamics including a shift to a more neuroprotective function as the brain ages. In Drosophila, glia are also implicated in regulating brain health and lifespan, underscoring a deep evolutionary conservation of glia function. The goal of this proposal is to determine how glia contribute to healthy brain aging and longevity using Harpegnathos saltator ants, a powerful model system to study the molecular and epigenetic regulation of aging. Adult Harpegnathos workers can become queens (called “gamergates”) via a phenotypic transition that results in a 5-fold extension of lifespan. We performed single-cell RNA-seq before and after the transition of workers to long-lived gamergates and found remarkable plasticity in the glia. Specifically, we found that ensheathing glia cells were substantially expanded in gamergate brains. Interestingly, gamergates retained high levels of ensheathing glia as they aged, whereas worker brains were rapidly depleted of these cells over the course of their life. Ensheathing glia cells respond to damage and provide general housekeeping and neuroprotective functions in Drosophila but they are not known to contribute to healthy brain aging and longevity. Our data suggest the hypothesis that an expanded ensheathing glia compartment contributes to the prolonged lifespan of gamergates. In Aim 1, we will determine the molecular and cellular changes that accompany the ensheathing glia dynamics during differential aging in worker and gamergates. In Aim 2, we will investigate the role of a specific receptor that is expressed in ensheathing glia cells and might directly regulate their expansion in response to the expression of a reproductive gene in gamergates. In Aim 3, we will utilize primary ant neuronal cultures and genetic manipulations in Drosophila to determine the causal link between ensheathing glia and longevity and its mechanism. Together, our work will elucidate 1) new molecular pathways that control glia plasticity, 2) a new biological role for glia plasticity, and 3) mechanisms for the regulation of healthy brain aging by glia.

PROJECT NARRATIVE Healthy brain aging is key to extend the healthspan and glia play an important role but the molecular pathways involved are poorly understood. We have discovered that changes in social status in Harpegnathos ants induce an expansion in neuroprotective phagocytic glia, which is linked to a 5-fold extension of lifespan. Here, I will define the molecular pathways that regulate these remarkable events of glia plasticity and how they impact healthy brain aging and longevity.