Fig. 1. Aberrant expression of Hh target genes in igu mutants and comparison with four other Hh signaling mutants. (A1-A7) Wild-type, (B1-B7) igu, (C1-C7) syu/shh, (D1-7) dtr/gli1, (E1-E7) yot/gli2 and (F1-F7) con embryos at 30 hpf. (A1-F1,A2-F2) Expression of nk2.2 in the ventral neural tube is reduced in all mutants. Only igu embryos retain a punctate nk2.2 expression (arrowheads in B1, inset is a higher magnification of boxed area). Lateral views are shown in A1-F1 and the respective cross-sections at the middle of the yolk extension are shown in A2-F2. (A3-F3) Expression of pax6 is ventrally expanded in yot/gli2 (E3) and con (F3), but not in other mutants. (A4-F4,A5-F5) Expression of en1 in somites is shown in lateral views and in cross-sections. en1 expression in MPs and MFFs is completely lost in con (F4, F5). A low level of expression persists in syu/shh (C4) and yot/gli2 (E4), and no defect of en1 expression is seen in dtr/gli1 mutants (D4,D5). In contrast to the other four mutants, en1 expression in somites is upregulated in igu embryos (B4,B5). (A6-F7,A7-F7) Expression of ptc1 is shown in whole mount and in cross-sections. Expression of ptc1 is reduced in syu/shh, dtr/gli1, yot/gli2 and con mutants (C7-F7). Expression is most severely reduced in con mutants, and is mildly reduced in the neural tube of syu/shh, dtr/gli and yot/gli2 mutants. Note that ptc1 expression is not maintained in somites of dtr/gli1 embryos, despite the presence of en1 expression, and that the ptc1 expression persists in the sclerotome regions of yot/gli2 (E7). In igu embryos, ptc1 expression is upregulated in the entire somites (B6, B7), whereas the expression in neural tube is unaffected or slightly reduced in the trunk, and slightly more reduced in the brain.