Expression of foo at later stages of development. Detection of foo transcripts in later stages of wild-type embryos. Expression is consistent with both NC cell and future pharyngeal pouch endoderm expression. (A-D) lateral view (top) and dorsal view (bottom) of foo expression at different stages of development. (A) 10- somite stage. (B) 15-somite stage; pharyngeal pouch endoderm of pp1 and pp2 are indicated. (C) 20-somite stage. (D) 26 hpf; broken red lines indicate location of sections shown in F,G. (E) Double in situ hybridization to krox20 and foo in a 10-somite stage embryo. Arrows indicate foo expression in streaming NC cells. (F) Transverse section of a 26 hpf foo in situ hybridized embryo through pp1. Arrow indicates endodermal pouch expression. (G) Transverse section of a 26 hpf foo in situ hybridized embryo through the post-otic region. Arrow indicates foo expression.