TREX1 and Aicardi-Goutieres syndrome: TREX1 (DNase III) is a major 3′ DNA exonuclease responsible for cytosolic DNA degradation (Morita et al., 2004), and TREX1 deficiency in the cytoplasm of patients with AGS leads to the accumulation of cytoplasmic DNA, which drives chronic inflammation caused by cGAS.