IFNB1 and Aicardi-Goutieres syndrome: TREX1 is an ER‐located exonuclease that digests both dsDNA and single‐stranded DNA, thereby preventing cGAS activation by degrading cytosolic DNA.[16, 17, 18]Trex1−/− fibroblasts and macrophages express elevated interferon‐stimulated genes, whereas Trex1‐deficient or Trex1‐nuclease‐deficient mice display Aicardi‐Goutières syndrome (AGS)‐like phenotypes, which can be reversed by the deletion of cGas, Mita or Ifnb1.