Fig. 2

cGAS colocalizes with cytosolic genomic DNA in SARS-CoV-2-induced syncytia. a Representative confocal immunofluorescence images of SARS-CoV-2-induced syncytia. HeLa-ACE2 cells were infected with SARS-CoV-2 at an MOI of 0.5. After 18 h, cells were fixed and stained for DNA with DAPI (blue) and viral nucleocapsid protein (NP) with anti-NP antibody (green). Triangles indicate budding chromatin (upper) or cytosolic chromatin (lower). Scale bar, 20 μm. b–d Quantification of cells for parameters as indicated. Cells were quantified for three different fields with at least 400 cells. Mean ± s.d., Data were pooled from 3 independent experiments. ****P < 0.0001, **P < 0.01, two-tailed Student’s t-test. CC cytoplasmic chromatin. e Representative images of cells stained for NP, DNA, and cGAS-Flag. cGAS-null HeLa-ACE2 cells reconstituted with cGAS-Flag were infected with SARS-CoV-2 at an MOI of 0.5 for 18 h, followed by staining with anti-NP antibody (green), DAPI (blue), and anti-Flag antibody (red) as indicated. Scale bar, 20 μm. f Cellular distribution of endogenous cGAS. HeLa-ACE2 cells (left) or cGAS-null HeLa-ACE2 cells (right) were stained with anti-cGAS antibody (red) and DAPI (blue). Scale bar, 20 μm. g HeLa-ACE2 cells were infected with SARS-CoV-2, followed by staining with anti-NP antibody (green), DAPI (blue), and anti-cGAS antibody (red) as indicated. Scale bar, 20 μm. h HeLa-ACE2 cells were treated as described in e and were stained with anti-NP antibody (green), DAPI (blue), and anti-phospho-STING (Ser366) antibody (red). Scale bar, 20 μm. i K18-hACE2 transgenic mice were infected with 10⁵ TCID₅₀ of SARS-CoV-2 for 3 days. Mouse lungs were harvested and subjected to immunohistochemistry analysis with anti-phospho-STING (Ser365) antibody (diaminobenzidine visualization). Nuclei were stained with hematoxylin (dark blue). Scale bar, 10 μm. j HeLa-ACE2 cells were treated as described in e and were stained with anti-NP antibody (green), DAPI (blue), and anti-IRF3 antibody (red). Scale bar, 20 μm