The phenotype of the most common human ADAR1p150 Za domain mutation P193A in mice is incompletely penetrant. The phenotype of the most common human ADAR1p150 Za domain mutation P193A in mice is incompletely penetrant

ADAR1 mediated A-to-I RNA editing is a self/non-self discrimination mechanism for cellular double stranded RNAs. ADAR mutations are one cause of Aicardi-Goutières Syndrome, an inherited paediatric encephalopathy, classed as a “Type I interferonopathy”. The most common ADAR1 mutation is a proline 193 alanine (p.P193A) mutation, mapping to the ADAR1p150 isoform specific Za domain. We report the development of an independent murine P195A knock-in mouse, homologous to the human P193A mutation. The Adar1P195A/P195A mice are largely normal and the mutation is well tolerated. Contrasting with previous reports when the P195A mutation was compounded with an ADAR1 null allele (Adar1P195A/-), we find a partially penetrant phenotype, with approximately half the animals being runted with a shortened lifespan and the remaining animals normal. Severe runting and shortened survival of Adar1P195A/- animals were partly associated with the parental genotype. The P195A mutation is well tolerated in vivo and the loss of MDA5 is sufficient to completely rescue phenotypes in the Adar1P195A/- mice. Overall design: Whole brain from 3-4 replicates of each genotype were subjected to RNA sequencing.