Targeting DNA polynucleotides in lupus

The goal of this proposal is to understand how the nucleic acid metabolizing enzyme TREX1 functions in human cells to process polynucleotides in the delicate balance between maintaining homeostasis and initiating host defense. The innate immune system has remarkable capacity to distinguish exogenous DNA polynucleotides of pathogens from endogenous cellular nucleic acids in order to protect humans from potentially dangerous viral and bacterial pathogens. This is an especially daunting biological challenge since billions of cells die every day in humans. These dying cells contain a 3.9 billion-nucleotide DNA genome that must be dismantled in an orchestrated process to prevent cellular nucleic acid sensors from inappropriately triggering activation of the immune system. Failure to efficiently dispose of DNA polynucleotides from dying cells is a key driver of nucleic acid-mediated innate immune activation and autoimmune disease, as exemplified by the presence of DNA-associated autoantigens in systemic lupus and lupus-like disorders. We generated Trex1 mutant transgenic mice by allelic replacement to test distinct mechanisms of dysfunctional exonuclease-mediated disease. Phenotypic and molecular analyses of Trex1 mutant mice will reveal the pathologic mechanisms of dysfunctional exonucleases. The selected Trex1 mutant alleles will allow us to discover the consequences of dominant vs. recessive genetics and contributions of catalytic vs. non-catalytic mutants to nucleic acid-mediated autoimmune disease. These animal models of autoimmunity will unmask the important cell-types and tissues of dysfunction, as well as the pathways of interferon-mediated innate immune activation and will reveal the sources of nucleic acid-mediated dysfunction driving disease pathogenesis. Determining these molecular and cellular mechanisms will uncover new opportunities for therapeutic targeting of DNA polynucleotides that initiate inflammation and autoimmunity.