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Fig. 2. Localization of X-hh transcripts during early development. Localizations of X-hh transcripts during development are revealed by in situ hybridization to embryos with antisense probes for X-bhh (A-D), X-shh (E-H), and X-chh (I-K). (A) Side view of an early gastrula embryo (stage 10), with animal hemisphere up. X-bhh transcripts are localized to the sub-epithelial layer of the entire marginal zone (arrow). (B) Anterior view of a neurula embryo (stage 14). X-bhh expression occurs throughout most of the neural plate, with strongest expression along the lateral border (arrows) and no expression along the midline (arrowhead). (C) Lateral view of a late neurula embryo, after neural tube closure (stage 19/20). The most prominent domain of X-bhh expression is in the anterior of the embryo (arrow), with more diffuse expression observed posteriorly in the mesoderm. (D) Lateral view of a tailbud embryo (stage 28) with anterior toward the left. High levels of X-bhh transcripts are seen in specific structures of the head including the eye (e), otic vesicle (ov) and branchial arches (ba). X-bhh transcripts are also localized in a chevron-shaped band within each somite, predominantly within the dermatome (see text; data not shown). (E) Side view of an early gastrula embryo (stage 10), with animal hemisphere up. X-shh transcripts are most prominent in the sub-epithelial layer of the entire marginal zone (the lower and upper arrows mark the dorsal and ventral sides of the embryo, respectively). With more extended incubation during the color reaction, lower level expression can be seen to extend over the animal hemisphere (not shown). (F) Anterior view of a neurula embryo (stage 14). X-shh expression is restricted to the presumptive midline (arrowhead) and is absent from the rest of the neural plate (arrows). (G) Lateral view of a late neurula embryo (stage 19/20) with anterior to the left. X-shh expression is in the notochord and ventral neural tube with the most prominent expression observed in an anterior domain (arrow). (H) Lateral view of a tailbud embryo (stage 29/30) with anterior toward the left. X-shh is expressed exclusively in cells of the notochord (n) and floorplate (fp) throughout the axis. Strong expression in the brain and other anterior structures persists. (I) Side view of an early gastrula embryo (stage 10), with animal hemisphere up. X-chh expression extensively overlaps that of X-bhh and X-shh and is most prominent in a band of cells within the marginal zone (arrow). (J) Top view of a mid-neurula embryo (stage 15/16) with anterior to the left. X-chh transcripts are most abundant in an extreme anterior domain of the embryo; the anterior portion of the neural plate is indicated by the arrows. (K) Lateral view of a tailbud embryo (stage 29/30) with anterior to the left. Low levels of X-chh transcripts are present in the pharyngeal cavity. (L) Side view of a tailbud embryo hybridized with a X-bhh sense probe as a control. |
