Fig. 1

Effects of suppressing pou5f3 on isthmus development. Embryos obtained by crosses of en-pou5f3+/− and wild-type fish were subjected to heat shock at the bud stage and the development of the isthmus was evaluated. A. Morphology of the isthmus at 25 hours post-fertilization (hpf) was assessed, followed by genotyping. Sibling embryos were normal (left), whereas isthmi of en-pou5f3+/− embryos were abrogated with no constriction (middle) or kinking (right). B–E. Expression of pax2a (B), fgf8a (C), wnt1 (D), and gbx2 (E) at 25 hpf in sibling or en-pou5f3+/− embryos with isthmic defects was examined by WISH, followed by genotyping. Except for gbx2 expression in embryos with a kinked isthmus, the expression of egr2b in rhombomeres 3 and 5 (r3 and r5, respectively) was examined in parallel. Solid and open arrowheads mark normal and affected isthmi, respectively. The residual fgf8a expression at the ventral MHB and ectopic expression of gbx2 in the forebrain are marked with arrows. All embryos revealed essentially the same phenotypes among the embryos of the numbers shown at the top-right. dm, dorsal midbrain; os, optic stalk; pa, pharyngeal arch; te, telencephalon. Scale bars, 100 μm.