Fig. 5. Effect of elevated Cv-2 expression on trunk neural crest cell migration. (A-E) Representative images of the trunk region of stage 16 chick embryos electroporated with pCIG (A,B) or co-electroporated with pCS2Cv-2 and pCIG (C-E) expression constructs at HH stage 10+. (A) In situ hybridisation with Sox10 of a control pCIG electroporated embryo. (B) Transverse section of embryo (A) at axial level indicated; black and white arrows identify equal progression of Sox10-positive migratory neural crest cells on control and electroporated sides. (C) In situ hybridisation with Sox10 of an embryo overexpressing Cv-2. The domain of Sox10 expression extends further caudally on the side overexpressing Cv-2 (right) than the control side (left). Insets in A and C show the distribution of GFP-positive cells, demonstrating the domain and efficacy of the electroporation prior to in situ hybridisation analysis; left side of the neural tube is the control; right side is the electroporated side. (D,E) Transverse sections through embryo (in C) as indicated by lines, with immunofluorescence labelling of HNK1. (D',E') Corresponding bright-field images in which the Sox10 signal is more easily seen. In the more anterior section (D,D') there is an increase in the number and distance of migration of HNK-1-positive migratory crest cells on the transfected side (black arrow) compared with the control side (white arrow). Sox10 signal is not detected in the ventral HNK1-expressing neural crest, perhaps owing to a decreased level of expression during ventral migration. In the more posterior section (E,E') Sox10- and HNK-1-positive crest cells have initiated migration on the Cv-2 electroporated side (black arrow) but not on the untreated side.