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Figure 1. Early expression of the Xenopus orthologue of the hairy related gene (XHey-1). Lateral (A,C,E,G) and dorsal (B,D,F,H) views of XHey-1 expression in tail bud and early tadpole stage embryos assayed by in situ hybridization. Anterior is to the right in all panels. A-F: In stage 22-28 embryos, expression is observed in the developing pronephros (yellow arrows and arrowheads), somites (red arrows and arrowhead), eyes, branchial arches, and in discrete regions of the brain (orange arrows and arrowheads). G,H: This expression pattern persists through stage 31. A notable exception occurs in the pronephros where XHey-1 expression decreases substantially at later stages and is subsequently not detectable in this tissue, despite robust expression elsewhere in the embryo.
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Figure 2. Xenopus orthologue of the hairy related gene (XHey-1) is expressed in the developing pronephric field in an overlapping pattern with other components of the Notch signaling pathway. The expression of Hey-1 is shown at stages 25 and 28 (A,F), and compared with both the expression of other components of the Notch signaling pathway (B-D,G-I) and with the pronephric anlage marker Lim-1 (E,J). Note that all four components of the Notch pathway shown here are expressed in an overlapping pattern, and this pattern is restricted to only the anterior-dorsal portion of the Lim-1 domain. This is the region of the pronephric anlage fated to contribute to the tubules. In all panels, embryos are viewed laterally with the anterior to the right.
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Figure 3. Later expression of the Xenopus orthologue of the hairy related gene (XHey-1) in comparison to Notch-1 and Serrate-1. XHey-1 expression persists in the somites (red arrows), head, eyes, and branchial arches of tadpole stage embryos shown from stages 32 to 35 (C,F,I). At this time, XHey-1 is also expressed in the heart (black arrows). Expression of Notch-1 and Serrate-1 is shown for comparison (A,B,D,E,G,H). Note that XHey-1 is expressed in a pattern largely overlapping that of Notch-1 and Serrate-1 in many tissues. However, unlike XHey-1, Notch-1, and Serrate-1 are expressed in the developing pronephros at this time (yellow arrows). In all panels, embryos are viewed laterally, with anterior to the right.
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jag1 (jagged 1) gene expression in Xenopus laevis embryo via in situ hybridization, NF stage 25, lateral view, anterior right, dorsal up, head r. and anterior trunk region only.
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jag1 (jagged 1) gene expression in Xenopus laevis embryo via in situ hybridization, NF stage 28, lateral view, anterior right, dorsal up, head and trunk region only.
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jag1 (jagged 1)gene expression in Xenopus laevis embryo via in situ hybridization, NF stage 32, lateral view, anterior right, dorsal up, head and trunk region only.
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jag1 (jagged 1)gene expression in Xenopus laevis embryo via in situ hybridization, NF stage 33, lateral view, anterior right, dorsal up, head and trunk region only.
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Fig. 4. Xenopus orthologue of the hairy related gene (XHey-1) is responsive to Notch signaling in the developing brain and pronephros. Embryos were injected with either GR-Su(H)VP16, GR-NotchICD, or GR-Su(H)D B M and induced with dexamethasone either early (between stages 11 and 13) or late (between stages 15 and 19). Injected embryos were cultured, fixed between stages 24 and 30, and processed for in situ hybridization. A: In the developing brain, XHey-1 is responsive to Notch signaling (between stages 11 and 19) independently of when signaling is perturbed. Activation of Notch signaling increases expression of XHey-1 on the injected side of the head [dark orange arrows; a,c; also see 4B (i,j)], whereas suppression of Notch signaling decreases expression of XHey-1 on the injected side of the embryo (dark orange arrows; b,d). B,C: In the pronephros, XHey-1 is responsive to Notch signaling; however, this responsiveness is sensitive to the time of induction of the injected con-
structs. These results can be compared with analysis of Lim-1 expression after perturbation of Notch signaling. Yellow and red arrows mark do- mains of the pronephric field (red tubule region, yellow duct region). Green arrows mark XHey-1 expression in the head region.
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Fig. 4. Xenopus orthologue of the hairy related gene (XHey-1) is responsive to Notch signaling in the developing brain and pronephros. Embryos were injected with either GR-Su(H)VP16, GR-NotchICD, or GR-Su(H)D B M and induced with dexamethasone either early (between stages 11 and 13) or late (between stages 15 and 19). Injected embryos were cultured, fixed between stages 24 and 30, and processed for in situ hybridization. B: Early activation of Notch signaling decreased both the expression of Lim-1 throughout the entire pronephric field (c,d) as well as the expression of Hey-1 (a,b). Activation of Notch signaling later, after the establishment of the initial Lim-1 pronephric field, decreases expression of only the duct domain of Lim-1 (g,h) while expanding the anterior expression of XHey-1 (c,d, and i,j).
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Fig. 4. Xenopus orthologue of the hairy related gene (XHey-1) is responsive to Notch signaling in the developing brain and pronephros. Embryos were injected with either GR-Su(H)VP16, GR-NotchICD, or GR-Su(H)D B Mand induced with dexamethasone either early (between stages 11 and 13) or late (between stages 15 and 19). Injected embryos were cultured, fixed between stages 24 and 30, and processed for in situ hybridization. C: Suppression of Notch signaling decreases Hey-1 expres- sion in embryos induced both early and late (a,b,e,f). In comparison, early suppression of Notch signaling has minimal effects on expression of Lim-1 (c,d). Later suppression of Notch signaling increases the expres- sion of duct specific markers, including the duct domain of Lim-1 (g,h).
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