Fig. 7. Transverse histological sections of wild-type and TIE-4 angiomotin E9.5 brains. Whole-mount PECAM-stained embryos were sectioned and stained with Hematoxylin and Eosin. (A) In wild-type brain, blood vessels align the neuroepithelium (arrows). (B) In contrast, the TIE-4 angiomotin brain has dilated blood vessels within the cephalic mesenchyme (arrows). This panel is representative of embryos 1-9 in Table 1. (C) Magnification of boxed area in A, showing capillaries residing and entering the neuroepithelium (arrowheads). (D) Magnification of boxed area in B, showing the presence of dilated blood vessels (open arrow) within the mesenchyme and with only a few capillaries entering the neuroectoderm (arrowhead). Note also the ruptured vessel (open arrow) with nucleated fetal blood cells leaking into the mesenchyme. (E) A more severe phenotype of a TIE-4-angiomotin mutant embryo displaying sack-like structures adjacent to the neuroepithelium (arrows), which has collapsed into the brain vesicle (asterisk). (F) Magnification of the boxed area in E, showing the dilated blood vessels. No vessel enters the neuroepithelium. cm, cephalic mesenchyme; ne, neuroepithelium. Scale bars: 125 µm.