Fig. 2. Premature neurogenesis in Mib1^–/– embryos. (A,B) Sagittal sections of wild-type (A) and Mib1^–/– (B) embryos at E9.5. The Mib1^–/– embryo has a smaller head, with picnotic cells in the brain and inside the ventricles. Enlarged views of the forebrain are shown in insets. (C-H) Sagittal and transverse sections of E9.0-E9.5 brain regions from wild-type (C,E,G) and Mib1^–/– (D,F,H) embryos. Sections were stained for nestin (C,D; in red) and huC/D (E-H; in red). BrdU incorporation (E,F; in green) and TUNEL staining (C,D,G,H; in green) were used for the detection of proliferative and apoptotic cells, respectively. Nuclear DNA was stained with Hoechst (in blue). (I) Impaired neurosphere formation in Mib1^–/– forebrains. Neural stem cells are absent in E9.5 (n=3) and E9.75 (n=5) Mib1^–/– forebrains. (J) Expression of neurogenin 1 (Ngn1), Dll1, Hes5 and Lfng in the neural tubes of E9.5 wild-type and Mib1^–/– embryos. (K,L) Neurogenin 1 (Ngn1) (K) and Neurod1 (L) expression in E9.5 wild-type (left) and Mib1^–/– (right) embryos. Note that the expression of both Ngn1 and Neurod1 in the trigeminal ganglia is increased in the Mib1^–/– embryos (arrows), and Ngn1 expression is also increased in the neural tube of the Mib1^–/– embryos (asterisk).