Fig. 4. Immunofluorescence confocal images of mouse spinal cords. (a) Cross-section at E12.5 of a wild-type (B⁺/B⁺) spinal cord stained for NMIIB (green) and N-cadherin (red). (b) Magnified view of a hypomorphic Arg709Cys NMIIB-mutant (B^CN/B^CN) spinal cord at E12.5 stained as in panel a. Note that the neuroepithelial cells have invaded and obstructed the spinal canal in the mutant mouse. (c) Apical border of the cells lining the spinal canal in a B⁺/B⁺ mouse at E11.5, showing a mesh-like adhesion structure stained for NMIIB (green) and β-catenin (red). (d) Spinal canal of an NMIIB-ablated (B^–/B^–) mouse at E11.5, showing collapse of the apical mesh-like structure, with neuroepithelial cells protruding into the canal, stained for NMIIB (green, which is not seen in the B^–/B^– mouse) and N-cadherin (red). These panels are reproduced with permission (Ma et al., 2007).