An Aicardi-Goutières Syndrome–Causative Point Mutation in Adar1 Gene Invokes Multiorgan Inflammation and Late-Onset Encephalopathy in Mice

• Published in: The Journal of immunology (1950) 2021-12, Vol.207 (12), p.3016-3027
• Main Authors: Inoue, Maal, Nakahama, Taisuke, Yamasaki, Ryuichiro, Shibuya, Toshiharu, Kim, Jung In, Todo, Hiroyuki, Xing, Yanfang, Kato, Yuki, Morii, Eiichi, Kawahara, Yukio
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.2100526

Aicardi–Goutières syndrome (AGS) is a congenital inflammatory disorder accompanied by overactivated type I IFN signaling and encephalopathy with leukodystrophy and intracranial calcification. To date, none of the mouse models carrying an AGS-causative mutation has mimicked such brain pathology. Here, we established a mutant mouse model carrying a K948N point mutation, corresponding to an AGS-causative K999N mutation, located in a deaminase domain of the Adar1 gene that encodes an RNA editing enzyme. Adar1K948N/K948N mice displayed postnatal growth retardation. Hyperplasia of splenic white pulps with germinal centers and hepatic focal inflammation were observed from 2 mo of age. Inflammation developed in the lungs and heart with lymphocyte infiltration in an age-dependent manner. Furthermore, white matter abnormalities with astrocytosis and microgliosis were detected at 1 y of age. The increased expression of IFN-stimulated genes was detected in multiple organs, including the brain, from birth. In addition, single-nucleus RNA sequencing revealed that this elevated expression of IFN-stimulated genes was commonly observed in all neuronal subtypes, including neurons, oligodendrocytes, and astrocytes. We further showed that a K948N point mutation reduced the RNA editing activity of ADAR1 in vivo. The pathological abnormalities found in Adar1K948N/K948N mice were ameliorated by either the concurrent deletion of MDA5, a cytosolic sensor of unedited transcripts, or the sole expression of active ADAR1 p150, an isoform of ADAR1. Collectively, such data suggest that although the degree is mild, Adar1K948N/K948N mice mimic multiple AGS phenotypes, including encephalopathy, which is caused by reduced RNA editing activity of the ADAR1 p150 isoform.