IRGM1 links mitochondrial quality control to autoimmunity

Mitochondrial abnormalities have been noted in lupus, but the causes and consequences remain obscure. Autophagy-related genes ATG5, ATG7, and IRGM have been previously implicated in autoimmune disease. We reasoned that failure to clear defective mitochondria via mitophagy might be a foundational driver in autoimmunity by licensing mitochondrial (mt)DNA-dependent induction of type I interferon (IFN-I). Here, we show that mice lacking the GTPase IRGM1 (IRGM homologue) exhibited a type I interferonopathy with autoimmune features. Irgm1 deletion impaired execution of mitophagy with cell-specific consequences. In fibroblasts, mtDNA soiling of the cytosol induced cyclic GMP-AMP synthase (cGAS)–Stimulator of Interferon Genes (STING)-dependent IFN-I, whereas in macrophages, lysosomal TLR7 was activated. In vivo, Irgm1(−/−) tissues exhibited mosaic dependency upon nucleic acid receptors. Whereas salivary and lacrimal gland autoimmune pathology were abolished and lung pathology was attenuated by cGAS and STING deletion, pancreatic pathology remained unchanged. These findings reveal fundamental connections between mitochondrial quality control and tissue-selective autoimmune disease.