Fig. 2

Fig. 2 Effects of RA on shh/vhh-1 expression in caudal floor plate cells and notochord. Embryos were treated with RA as in Fig. 1 and were fixed at 56 hr. (A) Residual expression of shh/vhh-1 in floor plate cells at the caudal end of control larvae at 56 hr. At this stage, there is no longer expression of shh/vhh-1 in the notochord. (B and C) Representative examples of shh/vhh-1 expression in RA-treated fish. The caudal-most floor plate cells (arrow) express comparatively higher levels of shh/vhh-1 compared to the same cells in controls. Patches of cells positive for shh/vhh-1 are located in what appears to be an extension of the notochord and/or cells in contact with the extension of the notochord (arrowheads). The caudal neural keel in RA-treated fish is thicker than that in controls. n, notochord; nk, neural keel. Scale bars, 50 μm.