Fig. 6. The nodal-related gene cyclops (cyc) is not required for medial floor plate development in the absence of spt function. sonic hedgehog (shh) expression in trunk medial floor plate (MFP) of wild-type (A) and mutant (B-D) embryos at 24 hpf. As noted already, spt^– MFP is often broader and some MFP cells are located ventral to the notochord (arrow) (C). In contrast, MFP is completely absent in the trunk of cyc^– embryos (B), but is significantly restored in spt^–;cyc^– embryos (D). Ventral brain shh expression in spt^–;cyc^– embryos is comparable to that in cyc^– embryos (data not shown); thus, suppression of the cyc^– MFP defect by the spt mutation is restricted to the trunk and tail. Lateral views, with anterior to the left. Scale bar: 100 µm.