Defects in endoderm and oral ectoderm in dkk1+ embryos (A–L, N–Q) Whole mount ISH, anterior to the left. (A–H) Dorsal and lateral views showing nkx2.3 expression in pharyngeal pouch endoderm at 50 hpf in controls (A, C, E, G), dntcf3+ (B, F), and dkk1+ (D, H) embryos. Normal pouches are numbered. Asterisks and black lines indicate defective pouches. (I–L, N–Q) Ventral views showing pitx2ca expression in control (I–L) and dkk1+ (N–Q) embryos. (M, R) Transverse sections of the mouth showing pitx2ca expression in control (M) and dkk1+ (R) embryos at 51 hpf. Arrowheads indicate expression in oral ectoderm. Dotted lines in K, L, P and Q indicate the mouth opening. White arrowhead indicates a ventral midline fold in the mouth. Scale bars: 100 µm.