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Fig. 3. Timing and pattern of the expression of Sonic Hedgehog, F-spondin and Xslug are shown by in situ hybridizations organized by type of preparation and by stage of development at fixation, in the case of embryos or peeled embryos (stage indicated at the lower right corner), or embryonic stage at which the preparations were made, in the case of explants (stage is indicated at the left or lower right corner); all explants shown were cultured to stages 24–27 and fixed for in situ hybridization. These data are discussed in the text. Panels D and E respectively show a sagittal and dorsal view of a whole embryo with a partially peeled neural plate. Anterior or dorsal is at the top in all images (NI: neural isolate; DI: dorsal isolate). The schematic below (V) qualitatively indicates that the percentage of neural isolate explants that contain cells specified to express SHH or F-spondin rises as the neural explants are cut later. By stage early neurula stages 13–14, all neural isolates express SHH or F-spondin at the midline. The minus signs indicate that neural explants are not yet specified to express a gene at a particular stage. |
