PROJECT SUMMARY Mitochondria are powerhouses of the cell that are often viewed as bacteria living in the cytosol. Stressed or damaged mitochondria induce inflammation through activation of multiple innate immune signaling pathways including the DNA sensing cGAS-STING pathway. We recently showed that deficiency of a cytoplasmic deglycosylase NGLY1 results in mitochondrial damage and potent activation of the STING pathway. Mutations in the NGLY1 gene are associated with an early childhood onset neurodegenetive disease with high mortality and no therapy. We recently established and characterized a Ngly1-deficient mouse model that develop early onset and progressive deteriorating coordination and motor functions. We also present exciting molecular and genetic evidence that implicate the mitochondrion-STING axis in neuropathology. The overall goal of this project is to define the neuro-pathological mechanism of NGLY1-deficiency, with a strong focus on the mechanism of the mitochondrion-STING axis. Aim 1 will define cell type specificity through genetic and single-cell approaches. Aim 2 will dissect intracellular signaling pathways in neuronal and glial cells. Aim 3 will evaluate therapies targeting the mitochondrion-STING axis. Studies proposed here should reveal the central mechanism of the mitochondrion-STING axis in neuropathology and neurodegeneration, which will have broad implications in many complex neurogenerative diseases that are affecting millions of people.