Genomic instability is a major driving force for cancer and age-related diseases. While DNA damage responses were long thought to regulate genome integrity and cell fates, evidence is accumulating that genomic instability also triggers inflammatory responses. Recent studies have provided insight into the mechanisms underlying such responses with the demonstration that the cytosolic DNA sensor, cyclic GMP-AMP synthase (cGAS), can play a key role in linking DNA damage to innate immunity. Interestingly, our research team has recently described the ability of human microglia and astrocytes to respond to foreign cytosolic double-stranded DNA and we demonstrated that human glia show robust levels of cGAS protein expression at rest and following activation. Furthermore, we showed these cell types constitutively express the critical downstream cGAS adaptor protein, stimulator of interferon genes (STING). In this R03 pilot study, we will begin to test the hypothesis that the cGAS-STING pathway detects cytoplasmic DNA in microglia and/or astrocytes after genotoxic stress and initiates glial auto- inflammatory responses. This project stems from a new collaboration between two experienced investigators with complementary expertise in the study of DNA damage repair mechanisms and glial innate immune sensor molecules. In these preliminary studies, we will determine whether genomic DNA damage elicits micronuclei formation and an elevation in the level of the cGAS product cGAMP in cultured glia, and we will correlate such responses with the production of auto-inflammatory mediators or potentially anti-tumor factors such as type I interferon. Furthermore, we will directly assess the relative importance of the cGAS-STING pathway in glial responses to DNA damage following pharmacological inhibition and/or CRISPR/cas9 genome editing. The proposed pilot R03 studies are an important first step in this new research direction and will provide a solid rationale for a more comprehensive investigation into the role of the cGAS-STING pathway in CNS cellular senescence and cancer for which future R01 mechanism support will be sought.
Recent evidence indicates that genomic instability can trigger inflammatory responses and the demonstration that the cytosolic DNA sensor, cGAS, can link DNA damage to innate immune responses raises the intriguing possibility that this molecule performs such a function in brain cells. In this R03 small grant mechanism application, we propose pilot studies to begin to test the hypothesis that cGAS detects cytoplasmic DNA in microglia and/or astrocytes after genotoxic stress and initiates potentially damaging inflammatory responses.
