SUMMARY. This proposal is in response to PAR-21-038: Stephen I. Katz Early Stage Investigator Research Project Grant. Aging is a major risk factor for the development of cognitive deficits and neurodegenerative diseases. Understanding the exact molecular mechanisms of brain aging and accelerated brain aging can lead to the development of novel interventions to delay or potentially reverse brain aging. Environmental factors including viral infections (such as SARS-CoV-2, the virus that caused the COVID-19 pandemic) have been shown to be associated with cognitive decline and accelerated brain aging. However, the exact molecular mechanisms underlying the effects of environmental factors, and specifically COVID-19, on brain aging remain unknown. Our long-term goal is to identify key factors that induce accelerated brain aging, so that therapeutics can be developed to delay or reverse brain aging. The overall objective of this proposal is to identify genes and regulators of gene expression that cause brain aging and accelerated brain aging in COVID-19 patients. Previous research from our group showed that many microRNAs (miRNAs), which are small non-coding RNAs that induce an orchestrated regulation of gene expression, are differentially expressed in the aged mouse brain and regulate aging. Based on those data and our recently published bulk RNA sequencing studies showing molecular signatures of brain aging in COVID-19 patients, our central hypothesis is that dysregulated gene and miRNA expression is an important facet of accelerated brain aging. Previous studies using microarray and bulk RNA sequencing approaches showed that aging induces distinct molecular signatures in the human frontal cortex. While layer enriched expression signatures have been identified in the human frontal cortex, the spatial topography of molecular signatures of aging remain largely unknown. Here, we will utilize state-of-the-art spatial transcriptomic technologies to analyze human frontal cortex sections from healthy individuals across lifespan, as well as frontal cortex sections from COVID-19 patients (and appropriate controls) to identify spatially distinct aging-regulated transcriptomic changes. We will investigate the effects of aging-regulated genes on cellular senescence using in vitro assays. To better understand regulatory mechanisms of aging-regulated gene expression, we will measure the expression of miRNAs in healthy individuals across lifespan and COVID-19 cases on similar frontal cortex sections and we will identify aging-regulated mRNA targets for candidate miRNAs. Finally, we will test the potential of miRNAs to accelerate and delay aging using in vitro assays and in vivo mouse models. These studies are expected to have a significant impact as they will determine novel targets for the development of therapeutics to delay or reverse brain aging and aging-related neuropathology. This proposal is highly relevant to public health and to the NIA’s mission of advanc...