Fig. 3. Neural tube defects. (A-C) Hoxb1 whole-mount in situ hybridization, labeling dorsal neural tube in the spinal region. Edges of open neuroepithelium are outlined in B. In C, the open cranial region (left embryo) is a procedural artifact. (D-F) Hematoxylin and Eosin stained sections through spinal neural tubes of E10.5 littermates. Embryo in E completed closure and embryo in F exhibited the intermittent neural tube closure phenotype. (G) Mitotic and apoptotic indices of neural tube sections (E10.5), assessed at similar spinal levels by phosphohistone H3 immunostaining and TUNEL. Each data point is the mean of positive/total cells on 12-16 sections per embryo, two embryos/genotype. Error bars indicate ±1 s.d.; P values were determined by Student's t-test.