Fig. 7

MDA-5 dependence of ADAR1 mutant growth inhibition, ISG expression, and brain pathology. A Adar^{D1113H /D1113H};ifih1^−/− double-mutant mice were generated by crossing the two mutant strains followed by genotype selections. In Adar^{D1113H /D1113H};ifih1^−/− double-mutant mice, the effect of Adar^{D1113H /D1113H} mutation was tested in mice without the presence of MDA-5. B, C Body weight of Adar^{D1113H /D1113H};ifih1^−/− double-mutant mice were measured separately for male and females from one to 7 weeks of ages. Both male and female mice did not exhibit growth retardation in comparison to WT mice. All comparisons at each age were non-significant as determined by Mann–Whitney U test (n = 7–20 per group). D ISG mRNA levels in Adar^{D1113H /D1113H};ifih1^−/− double-mutant mice, as well as in Adar^{K999N /K999N};ifih1^−/− double-mutant mice (E), were compared to WT mice. ISG levels in double-mutant mice were significantly lower than in the mutant mice and not different from the wildtype control mice. One-way ANOVA with Tukey adjustment for multiple comparisons, n = 4–5 per group; p < 0.001; ****p < 0.0001. F Formalin fixed paraffin embedded (FFPE) sections of 8-week-old mice were stained with hematoxylin and eosin (H&E) (left) or in situ hybridization (ISH) for ISG-15 (middle) or CXCL10 (right). Cortical sections (CTX) show no evidence of inflammatory infiltrate on H&E stain in WT or mutant mice. ISH in WT and double-mutant mice showed no labeling of cortical neurons for ISG-15 (middle) and microglia for CXCL10 (right). G Deep gray matter sections (V = lateral ventricle, CP = choroid plexus) showed no evidence of inflammatory infiltrate on H&E stain in WT or double-mutant mice. ISH in WT and double-mutant mice showed no labeling of cortical neurons and ependyma for ISG-15 (middle) and microglia and ependyma for CXCL10 (right). Bar = 100 microns