XB-IMG-132150
Xenbase Image ID: 132150
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Fig. 3. Xlhbox-8 expression relies on TGF-b and FGF signals. (A) At the 1-cell
stage, synthetic mRNA encoding inhibitory proteins were injected into the vegetal
pole. At stage 9, vegetal pole explants were dissected and cultured to the mid-tailbud
period (stage 33-36). RNA levels were assayed by RT-PCR. (B) Both a truncated
activin (tAR) and truncated FGF receptor (XFD) block expression of Xlhbox-8 but a
truncated BMP receptor has no effect. IFABP expression is unaffected by all three
truncated receptors. 4-5 nanograms of mRNA for each receptor was used in this
experiment and the result does not differ from experiments using 400-500 picograms
of mRNA except that the truncated BMP receptor does not efficiently induce cardiac
actin expression at 400 picograms (data not shown). (C) Induction of the ectodermal
markers NCAM and epidermal cytokeratin in vegetal poles expressing a truncated
activin receptor. The activin-specific antagonist follistatin (XFS) neuralizes vegetal
poles but does not induce expression of epidermal cytokeratin. 2 nanograms and 500
picograms of mRNA were used in the truncated activin receptor and follistatin
injections, respectively. (D) A dominant negative form of RAS (2 nanograms) blocks
expression of Xlhbox-8 but has no effect on IFABP expression. The activin-specific
antagonist follistatin has no effect on the expression of either IFABP or Xlhbox-8.
Neither follistatin nor the dominant negative RAS induce expression of the
mesodermal marker cardiac actin. (E) The follistatin mRNA used in parts C and D of
this figure blocks induction in animal caps by injected activin mRNA as judged by
expression of the pan-mesodermal marker Brachyury (Xbra). 1 nanogram of mRNA
encoding follistatin was co-injected with 2 picograms of mRNA encoding activin
bB. WE lanes represent RT-PCR products where mRNA from an unmanipulated
embryo was used for cDNA synthesis. The WE-RT lanes represent assays in which
reverse transcriptase was left out of the cDNA synthesis step with whole embryo
RNA as a template. This serves as a control for DNA contamination. Elongation
factor 1 alpha (EF-1a) is included as a control to insure that similar amounts of RNA
are used in each lane. Image published in: Henry GL et al. (1996) Copyright © 1996. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View |