Fig. 2: Brain endothelial cells express SARS-CoV-2 receptors in mice and humans.

a, RNA-seq in single mouse brain cells characterized the cell-type-specific expression of the SARS-CoV-2 receptors Ace2, Bsg and Nrp1. Colors represent mean gene expression, and diameters denote the percentage of positive cells in the 20 cell clusters. Uniform manifold approximation and projection (UMAP) plot and dot plot for marker genes are shown in Extended Data Fig. 3. b, Representative images of mouse brain co-stained for ACE2, BSG, NRP1, the endothelial markers CD31 or caveolin-1 and the pericyte marker PDGFRβ. BSG and NRP1 were co-localized with caveolin-1 or CD31, respectively, but not with PDGFRβ. The staining was reproduced in at least six mice for each marker. Noteworthy, in the scRNA-seq analysis, the number of Ace2 mRNA-positive cells was low and did not fully reflect the number of ACE2-positive cells identified by immunostainings. In immunostainings, almost all pericytes and tanycytes⁵⁹ were positive for ACE2, in contrast to the scRNA-seq data. Scale bars, 5 µm. VLMCs, vascular and leptomeningeal cells; OPCs, oligodendrocyte progenitor cells. c, Cell-type-specific expression of ACE2, BSG and NRP1 in a previously published single nuclear RNA-seq profile of human brain²⁸. Gene expression of ACE2, BSG and NRP1 is shown as dot plots for all 30 clusters. UMAP plot and dot plot for marker genes is shown in Extended Data Fig. 4. d, Representative images of the human frontal cortex co-stained for ACE2, BSG and NRP1 with the endothelial marker CD34 confirmed the cell-type-specific localization of the receptors in the vascular unit. ACE2, BSG and NRP 1 were co-localized with the endothelial protein CD34. Images were obtained from a dataset of three patients (three sections per patient). Scale bars, 5 µm. e, Human brain endothelial hCMEC/D3 cells were transfected with human ACE2 and were incubated with SARS-CoV-2 (multiplicity of infection (MOI) of 1). Twenty-four hours after exposure to the virus, the spike glycoprotein was detected in several ACE2-positive cells indicating infection. The experiment was performed three times. Scale bars, 5 µm. f, dsRNA was found in caveolin-1-positive endothelial cells in the cortex of two of four patients with COVID-19 but not in three uninfected controls. Scale bar, 20 µm and 2 µm (inset).