DNA damage-induced cGAS signaling in Alzheimer's disease This application is being submitted in accordance with NOT-AG-20-034. Studies proposed in this administrative supplement request to our funded NIH grant 1R01AI148741 (Non-canonical cGAS signaling in DNA damage response) will provide novel functional insights into whether DNA damage-driven cGAS signaling activity contributes to pathogenesis of AD. Alzheimer's disease (AD) is the most common form of dementia, accounting for about 60-70% of all the dementia worldwide. Persistent accumulation of DNA damage, one of the hallmarks of aging, has been linked to AD and numerous neurodegenerative conditions. Accumulation of elevated DNA double-strand breaks (DSBs) in post- mortem AD patient brain tissue has been reported by multiple studies. Additionally, multiple pre-clinical mouse models have revealed that increased DNA damage and associated molecular signatures are observed in the brain, and that appearance of these evidence precedes the onset of neurological symptoms or neurodegeneration in these animal model. Interestingly reducing DNA damage in animal models has been shown to ameliorate pathological features of AD. A better understanding of the mechanisms regulating DNA damage signaling in brain, in the context of AD holds potential for identifying therapeutic targets for the disease. The innate DNA sensor, cyclic GMP–AMP synthase (cGAS), has recently emerged as a critical responder to DNA damage wherein cGAS activation initiated by the damaged DNA triggers inflammation and apoptotic pathways via DDR induction. In this supplement request, we propose to provide new functional insights into whether DNA damage-induced cGAS signaling activity contribute to pathogenesis of AD. This objective will be addressed via following Specific Aims: 1. Determine the abundance, activation status and distribution of constituents of cGAS signaling brain tissue from donor AD patients and preclinical mouse models of AD. 2. Determine the involvement of cGAMP-STING signaling in Aβ-exposed in microglia cell cultures. Overall, these studies will introduce the role of cGAS signaling in AD and provide a molecular rationale for targeting cGAS-STING-driven interferon and DNA damage response signaling in preclinical mouse models. As such, this supplement request is within the scope of the active parent NIH award and has the potential to stimulate new studies for examining novel molecular and biochemical mechanisms of cGAS-STING pathway in AD. We predict that establishing this new pathway in AD will stimulate additional activity on the part of neuroscientists, immunologists and cell biologists thereby leading to progress in deciphering and potentially treating AD and related dementias. This supplement will also enable our laboratory to develop a focus on AD by generating additional experimental data that can be leveraged to submit new proposals focused directly on AD.