Mice lacking PDPN or CLEC-2 develop aneurysms and spontaneous hemorrhages in the diencephalon at midgestation. (A) Quantification of PDPN expression from confocal images of mouse embryonic diencephalon, with values representing 3 experiments. Bars represent percentages of bleeding onset in the Pdpn^−/− diencephalon. (B) The E12.5 mouse brain. (C) Representative images of hematoxylin and eosin–stained embryonic coronal sections of the diencephalon. Arrows indicate aneurysms. (D) Confocal images of lower diencephalon aneurysm-like radial sprouts. IB4 marks the vasculature. TER119 marks erythrocytes. Thromb marks eMks and platelets. Neural, brain tissue. (E) Confocal images of angiogenic sprouting into the diencephalon (red boxes). The bar graph on the right represents the ratio of radial sprouts in the mutant diencephalon compared with the paired WT. (F) Confocal images of aneurysm-like sprouts in the diencephalon. Bar graph on the right represents the percentage of dilated sprouts (>15 μm in diameter) throughout mutant diencephalons relative to WT. Scale bars, 100 μm (C,E); 25 μm (D); and 20 μm (F). Data are means ± standard error of the mean; n, number of embryos. *P < .05; **P < .01.