CGAS and viral infectious disease: Consistent with previous studies showing that intrinsic apoptosis deficiency induces the IFN response by mitochondrial DNA (mtDNA)-dependent activation of the cGAS-STING pathway in basal or virus infection conditions30,31, our results showed the constitutive expression of numerous IFN-stimulated genes (ISGs) in Apaf-1−/− MEFs compared to WT MEFs in the resting state.