Integrin β8 is expressed in periventricular cells of the embryonic brain. (A,B) Whole-mount in situ hybridization analyses shows integrin β8 mRNA expression in tissues surrounding the ventricles of E10.5 embryonic brain (A, antisense; B, sense). (C,D) Transverse sections of E12.5 brains hybridized with integrin β8 antisense (C) or sense (D) probes showing localization of integrin β8 to periventricular cells in the neuroepithelium. (E,F) Similar areas to those shown in C at E12.5 (C, box E and box F) are shown at a higher magnification in an E13.5 brain hybridized with an integrin β8 antisense probe (E,F). Note the absence of integrin β8 mRNA from the vascular cells of the brain (A) and inside of the brain area (C,E). Scale bar: 500 μm in C and D; 200 μm in E,F.