Fig. 9. The foo mutation affects pouch formation. Right panels, foo/foo homozygote embryos; left panels, same-clutch wild-type siblings. (A) zn-8 antibody staining of a wild-type embryo at 34 hpf. Pharyngeal pouches (pp1-pp4) are indicated by arrowheads as in Fig. 8. (B) zn-8 antibody staining of a 34 hpf foo/foo embryo. The posterior pouches pp2-4 are substantially reduced, whereas pp1 is only mildly affected. (C) nkx2.3 expression by in situ hybridization of a 30 hpf wild-type embryo. (D) nkx2.3 expression in a 30 hpf foo/foo embryo. Most of the nkx2.3 expression is absent or disorganized. (E) pax8 expression in a 21-somite wild-type embryo with pp2 indicated as in A. (F) pax8 expression in a 21-somite foo/foo embryo. Expression of pax8 in pp2 is absent and the otic vesicle is substantially reduced.