Ptk7 expression correlates with tissue defects in chuzhoi. (A-C) Wholemount in situ hybridisation for Ptk7 expression over the time of neurulation reveals robust staining in the caudal region and less intense staining elsewhere; dorsal (A, B) and lateral (C) views of embryos at early somite stage (A), 4 somite stage (B) and E9.5 (C). (D-G) Immunofluorescence with anti-Ptk7 antibody on transverse sections of E8.5 embryos around the site of closure 1. Ptk7 protein is detected in the cell membranes of both mesoderm and neuroepithelium, in both wild-type (D, E) and chuzhoi mutants (F, G), although the level of expression is much reduced in chuzhoi mutants; exposure times of these images were 57 ms (D) and 192 ms (F). (H, I) Slide in situ hybridisation at E12.5 detects Ptk7 transcripts in the developing eye and eyelid epithelium (arrows, H), and intensely in the lung epithelium (arrows, I).