snRNA-seq analysis and additional characterization of BBB breakdown in E4F and E3F mice. (A) UMAP space representing 10 distinct clusters obtained via unsupervised clustering analysis. (B) Dot plot reporting cell type–specific markers used to define the clusters. (C) Proportion of nuclei included in each cluster. (D) Heatmap showing average expression values of vascular cluster signature genes in selected vascular-associated cell types, including PCs, aSMCs, capillary endothelial cells (capilEC), and arterial endothelial cells (aEC), as well as microglia (MG) and astrocytes (AC) according to the mouse brain vascular atlas (Vanlandewijck et al., 2018). Nuclei included in vascular signature groups 1 (violet) and 5 (cyan) were defined as ECs and PCs, respectively. Data in A–D are from 16 mice. (E) Quantification of Ktrans values in the hippocampus (Hipp) of 2–3-, 4–6-, and 9–12-mo-old E4F and E3F mice. (F) Quantification of fibrinogen in the hippocampus of 2–3-, 4–6-, and 9–12-mo-old E4F and E3F mice. (G) Quantification of PC coverage in the hippocampus of 2–3-, 4–6-, and to 9–12-mo-old E4F and E3F mice. Mean ± SEM. n = 6-8 mice per group (E); n = 4–5 mice per group (F and G). Significance by one-way ANOVA with Bonferroni post hoc test. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. OPC, oligodendrocyte precursor cells.