Fig. 1

Micronuclei formation in syncytia induced by SARS-CoV-2 spike expression. a Schematic representation of cell–cell fusion induced by ACE2-spike interaction to form a multinucleated syncytium. b Expression of ACE2 and spike proteins 24 h post transfection detected by Western blot. c Quantification of syncytia formation upon expression of spike glycoprotein in Hela-ACE2 cells. Data are mean ± SD of 4 fields (10 × objective lens). ****P < 0.0001. d Representative images captured on Hela-ACE2 cells 24 h post transfection. Nuclei were stained with DAPI. White dashed lines depict shape of target syncytium and the white arrows indicate micronuclei. Scale bars: 50 μm for the left images, 20 μm for zoomed images on the right. e The formation rate of micronuclei in vector transfection cells, spike protein transfection cells and syncytia, respectively. Data are mean ± SD of 5 fields (20 × objective lens). ****P < 0.0001. f Enumeration of micronuclei formation per syncytium. On average, each syncytium cell has 3.99 micronuclei, n = 104. g The number of micronuclei were positively associated with the nucleus number of syncytia. Analysis was performed by Spearman rank correlation