Fig. 2. Disorganized structures of the Hes-mutant nervous system. (A-D) Toluidine Blue staining of sections at the level of rhombomere 7 of wild-type (A), Hes1^–/– (B), Hes5^–/– (C) and Hes1^–/–;Hes5^–/– (D) at E10.5. Only Hes1^–/–;Hes5^–/– neural tube is morphologically abnormal. In these panels, dorsal is up. (E-J) SEM analysis was performed with E10.5 mouse embryos. (E,F,I) In the wild type, radial glial cells are aligned radially in the wall of the neural tube. Their endfeet form a smooth inner surface. (G,H,J) In Hes1;Hes5 double mutants, cells are exposed to, and scattered into, the lumen. As a result, the cell arrangement is totally destroyed. In addition, cells become round in shape (J, compare with I). Boxed regions in (E,G) are enlarged in (I,J). (K) Positions of (E-H) are indicated. Scale bars: 100 µm in A-H; 10 µm in I,J.