Fig. 1.

Grhl2 mutant NNE exhibits loss of epithelial integrity and increased mesenchymal properties. (A-D) H&E staining of transverse sections of cranial neural folds of 13-somite mouse embryos shows tightly associated wild-type NNE (A,C, arrows) versus the loosely associated epithelium and altered cellular phenotype of Grhl2 mutant NNE (B,D, arrows). (E,F) Immunostaining shows regular, punctate ZO-1 (green arrows) and low-level vimentin expression in wild-type NNE (E) versus an irregular ZO-1 expression pattern and aberrant vimentin (red arrows) in Grhl2 mutant NNE (F). (G-J) Quantitation of A-F. (G) NNE breaks in Grhl2 mutants (seven embryos, 50 sections each) are increased compared with wild type (five embryos, 50 sections each). (H,I) The number of ZO-1 puncta per 100 µm shows greater spread and overall smaller mean (H) and the distance between puncta is greater in Grhl2 mutant embryos than in wild type (I). (J) Vimentin expression is increased in Grhl2 mutant NNE compared with wild type. Experiments were performed on four embryos per genotype, ten sections each. Mean±s.d. **P<0.001, ***P<0.0001, Student's t-test. FB, forebrain; HB, hindbrain; RSC, rostral spinal cord; NNE, non-neural ectoderm; WT, wild type. Scale bars: 20 µm.