Modeling of TREX1-Dependent Autoimmune Disease using Human Stem Cells Highlights L1 Accumulation as a Source of Neuroinflammation

Three-prime repair exonuclease 1 (TREX1) is an anti-viral enzyme that cleaves nucleic acids in the cytosol, preventing accumulation and a subsequent type I interferon-associated inflammatory response. Autoimmune diseases, including Aicardi-Goutières syndrome (AGS) and systemic lupus erythematosus, can arise when TREX1 function is compromised. AGS is a neuroinflammatory disorder with severe and persistent intellectual and physical problems. Here we generated a human AGS model that recapitulates disease-relevant phenotypes using pluripotent stem cells lacking TREX1. We observed abundant extrachromosomal DNA in TREX1-deficient neural cells, of which endogenous Long Interspersed Element-1 retrotransposons were a major source. TREX1-deficient neurons also exhibited increased apoptosis and formed three-dimensional cortical organoids of reduced size. TREX1-deficient astrocytes further contributed to the observed neurotoxicity through increased type I interferon secretion. In this model, reverse-transcriptase inhibitors rescued the neurotoxicity of AGS neurons and organoids, highlighting their potential utility in therapeutic regimens for AGS and related disorders. Thomas et al. used human pluripotent stem cells to dissect the contribution of neurons and glia to the neuroinflammatory disorder Aicardi-Goutières syndrome (AGS). They found that mutant cells accumulate retroviral-like extrachromosomal nucleic acids that trigger a neurotoxic response, and they suggest that anti-retrovirals could potentially provide therapy for this disease.