SRP404826 PRJNA894940 GSE216673 TREX1 is required for microglial cholesterol homeostasis and subsequent oligodendrocyte maturation during brain development [scRNA-seq] Three Prime Repair Exonuclease 1 (TREX1) gene mutations have been associated with Aicardi-Goutières Syndrome (AGS) - a rare, severe pediatric autoimmune disorder that primarily affects the brain and has a poorly understood etiology. Microglia are brain-resident macrophages indispensable for brain development and implicated in multiple neuroinflammatory diseases. However, the role of TREX1 - a DNase that cleaves cytosolic nucleic acids, preventing viral- and autoimmune-related inflammatory responses - in microglia biology remains to be elucidated. Here, we leverage a model of human embryonic stem cell (hESC)-derived engineered microglia-like cells, bulk, and single-cell transcriptomics, optical and transmission electron microscopy, and three-month-old assembloids composed of microglia and oligodendrocyte-containing organoids to interrogate TREX1 functions in human microglia. Our analyses suggest that TREX1 influences cholesterol metabolism, leading to an active microglial morphology with increased phagocytosis in the absence of TREX1. Notably, regulating cholesterol metabolism with an HMG-CoA reductase inhibitor, FDA-approved atorvastatin, rescues these microglial phenotypes. Functionally, TREX1 in microglia is necessary for the transition from gliogenic intermediate progenitors known as pre-oligodendrocyte precursor cells (pre-OPCs) to precursors of the oligodendrocyte lineage known as OPCs, impairing oligodendrogenesis in favor of astrogliogenesis in human assembloids. Together, these results suggest routes for therapeutic intervention in pathologies such as AGS based on microglia-specific molecular and cellular mechanisms. Overall design: Samples represent five independent preps of 100-day-old assembloids of microglia co-cultured with oligodendrocyte-containing cortical neural organoids. Microglia and organoids were generated from the H9 human embryonic stem cell (hESC) line. Two microglia genotypes were tested: control (WT) and CRISPR-edited TREX1 mutant (KO) microglia. Three independent assembloid preps were generated (1, 2, and 3). We used AmpliDrop single-cell RNA-seq (scRNA-seq) technology to characterize these assembloids and interrogate the role of human TREX1 variants in early brain development. GSE216673 pubmed 38129659 parent_bioproject PRJNA895041