Fig. 4. Morphology of the spinal nerves in control and mutant embryos, on E12.5 and E13.5. (A-H) ß-Galactosidase activity was detected in whole-mount preparations. Lateral view of control embryo (A) showing intense labelling of craniofacial structures and PNS. The mutant (B) displays an absence of labelling in the trunk PNS. The 200 µm transverse sections of whole-mount E13.5 control (C) and mutant (D) embryos reveal the loss of reporter gene expression in the distal part of the mutant innervation network (white arrows in D). (E-H) Detail of cutaneous lateral ramus and lateral muscular innervation. The immunolocalisation of NF-160 on similar 200 µm transverse sections from control (E,F) and mutant (G,H) embryos shows the presence of nerves in both cases. However, SC have been specifically lost from the distal part of the mutant nerves (black arrowhead in G,H).