XB-IMG-132186
Xenbase Image ID: 132186
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Figure 5. Dll4 acts as a Notch ligand in Xenopus embryos. One
blastomere of 2-cell albino embryos was injected with either (a)
nLacZ RNA and 0.1–0.25 ng of Dll4 RNA, or (b) nLacZ RNA
only. At stage 14, the embryos were fixed, stained in whole
mount with X-gal (light blue reaction product), and then labeled
by in situ hybridization for the expression of N-tubulin (dark
blue). Embryos are presented anterior to the left with the injected
side on the top. Note that N-tubulin expression is suppressed
in the area of Dll4 injection (as visualized with lacZ). (c)
Results of RNase protection assay to measure the levels of
ESR-1 and ESR-7, targets of Notch signaling, in neural ectoderm
isolated from embryos injected with the indicated RNAs. Ectoderm
was neuralized by injection of Noggin. RNAs were extracted
at stage 13 and the ability of Dll4 to activate Notch
targets were examined. For quantification, specific band intensities
in each lane were normalized to the amount of EF1-a
RNA to control for sample recovery, and the gene expression
results are represented relative to the uninjected controls. Note
that Dll4 weakly activates ESR-1 and ESR-7 expression via endogenous
X-Notch activation (column 3), whereas ESR gene activation
by Dll4 is strongly potentiated by coinjection of murine
Notch1 (column 4) to reach the levels induced by X-Delta1 (column
5). In a separate experiment (columns 7–10), the ability of
Dll4 to signal through the murine Notch4 receptor was tested.
The activation of ESR-1 and ESR-7 expression by Dll4 (column
9) is strongly potentiated by coinjection with murine Notch4
(column 10). In both experiments, activation of targeted genes
was increased >3.5-fold upon coinjection of Dll4 with either
murine Notch1 or Notch4. Image published in: Shutter JR et al. (2000) Copyright © 2000. Image reproduced on with permission of the Publisher, Cold Spring Harbor Laboratory Press. This is an Open Access article.
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