Fig. 4: In adult inhibition of endothelial γ-secretase activity is sufficient to generate IB4⁺ vascular abnormalities.

a Schematic representation of a mouse model with adult inhibition of endothelial γ-secretase activity. Psen1^loxP/loxP; Psen2^–/– mice were injected with cerebral endothelium-specific adeno-associated control (AAV-BR1-Control; C) or Cre recombinase-expressing (AAV-BR1-Cre; Cre) viruses. b Schematic representation of the qPCR amplicon used to detect the Psen1 excised allele (orange bar). Right graph: Quantification of the degree of Psen1 excision (a.u., arbitrarty units) in the striatum of C and Cre mice. Mean ± SEM. n = 3 C and 10 Cre mice; Student’s t-test. c Striatal confocal XY images from C and Cre mice stained with endothelial (IB4; red) and Psen1 (ISH; brown) markers. Scale bar = 20 µm. d Quantification of endothelial Psen1⁺ signal in the striatum (left graph) and the cortex (right graph) of C and Cre mice. Mean ± SEM. n = 4 mice; Student’s t-test. e–g Confocal projections of striatal (e) or hippocampal slices (f, g) from Psen1^loxP/loxP; Psen2^–/– mice injected with AAV-BR1-Control or AAV-BR1-Cre viral vectors, and, 2 months later, perfused with Evans blue (EB; white —e) and stained with endothelial (IB4; red —e, g— or green —f), pericyte (PDGFRß; red —f), astrocytic end-feet (AQP4; green —g), and nuclear (DAPI; blue) markers. Scale bars = 40 µm. Right graphs are the quantification of: e percentage of area occupied by IB4⁺ in C and Cre mice in hippocampus (upper row) and striatum (lower row). Mean ± SEM. n = 3 mice; Student’s t-test. f, g Percentage of area occupied by PDGFRß⁺ (f) or AQP4⁺ (g) signal (in distal —D— vessels and in IB4⁺ area) in hippocampus form C and Cre mice. Mean ± SEM. n f = 3 C and 5 Cre mice; n g = 4 C and 6 Cre mice ANOVA, post hoc Tukey’s test.