Epitranscriptomic Regulation of Microglia in Alzheimer's Disease - Project Summary Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by memory loss and cognitive impairment which constitutes the most common type of dementia and impacts nearly 6 million people in the US. AD has a complex etiology which includes genetic contributions, environmental factors, and age- associated changes in the brain. In addition, brain inflammation has emerged as a key factor in the development and progression of AD. Thus, understanding the brain’s inflammatory response is critical for comprehending the factors that contribute to AD as well as for identifying biomarkers and novel therapeutic targets. Within the brain, microglial cells are the major cell type that mediate the response to neuroinflammation. These cells normally exist in a resting state but then become activated in response to inflammatory stimuli. At early stages of disease, microglial activation plays a beneficial role by releasing anti-inflammatory cytokines and contributing to the clearance of pathogenic protein aggregates that accumulate in the AD brain. However, prolonged microglial activation causes the release of neurotoxic factors and excessive synaptic pruning, promoting disease progression. Thus, understanding the factors that control the transition from a resting to an active microglial state and elucidating how microglial function is regulated during AD pathogenesis is crucial for determining how this critical cell type contributes to disease, as well as for developing novel microglial-targeting therapeutics. One mechanism that the brain uses to control gene expression is methylation of adenosine residues in mRNA to form m6A. The m6A modification is found in thousands of transcripts and enables fine-tuning of gene expression in response to a variety of stimuli and cellular states. In addition, m6A and its regulatory proteins are altered in the brains of AD patients. Here, we will explore the hypothesis that dynamic regulation of m6A contributes to gene expression changes that underlie microglial cell activation in response to inflammation. Using new technologies developed in our lab, we will identify for the first time the m6A sites that undergo dynamic methylation in microglia during AD progression (Aim 1). Then, we will uncover the proteins in microglia that bind to m6A and investigate how microglial activation alters RNA:protein interactions (Aim 2). Finally, we will determine how microglial- specific depletion of m6A contributes to microglial function and AD progression using a novel mouse model (Aim 3). Altogether, these studies will be the first to explore m6A dynamics in microglial cells in vivo during AD and will provide new knowledge of the role of m6A in microglial activation and AD progression.
