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Fig. 1. Fgf signalling is necessary for proper LPM pattern. Foxf1, hand1, sall3 and Xbra were assayed for a response in expression domain when Fgf signalling was inhibited with SU5402. The anterior domain, marked by foxf1 expression (A–D), was expanded toward the ventral side of the embryo (arrowheads in A and B), and was upregulated at the posterior end of the LPM just ventral to the blastopore (arrowheads in C and D). The posterior border of hand1 (E–H) is displaced further posterior, particularly at the dorsal edges of the domain (arrowheads in E–H). The LPM domain of sall3 (I–L) is displaced posterior with a loss of Fgf signalling (white arrowheads in K and L) while the posterior neural tube domain is undetectable (black arrowheads in K and L). Expression of Xbra in the tailbud domain is completely lost in the absence of Fgf signalling (arrowheads in M and N). llv: left lateral view, embryos oriented with the anterior pole toward the left of the image, dorsal at top. pos: posterior view, embryos oriented with dorsal at top of image. The total number of embryos examined for each panel is indicated in the lower left hand corner. |
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Fig. 9. Loss of retinoic acid signalling partially rescues effects of loss of Fgf signalling on the domains of isl1 and Xbra. Decreasing RA signalling in SU5402 treated embryos had little effect on the nkx2.5 domain (D) as it was still present in a highly restricted domain similar to the SU5402 treatment (C). However, a loss of Fgf signalling leads to a loss of isl1 (H) and Xbra (T), while neither domain is changed when RA signalling is lost (F and R). However, when Fgf signalling is decreased in conjunction with reduced RA signalling both isl1 and Xbra expression is detectable in their normal domains (H and T). However, the restriction of the hand1 expression domain under reduced RA condition (J and N) seems to be dominant to the extended domain seen in the SU5402 treated embryos (K and O) as losing both RA and Fgf signalling (L) leads to a restricted domain similar to the RA antagonist alone.
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| Gene |
Clone |
Species |
Stages |
Anatomy |
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foxf1
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laevis
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NF stage 28
to
NF stage 29 and 30
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pharyngeal arch
,
lateral plate mesoderm
,
anterior dorsal lateral plate region
,
olfactory region
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hoxc10
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laevis
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NF stage 28
to
NF stage 29 and 30
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presomitic mesoderm
,
somite
,
tail bud
,
lateral plate mesoderm
,
posterior
,
[+]
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tnni3
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laevis
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NF stage 28
to
NF stage 29 and 30
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heart
,
cardiac mesoderm
,
primary heart field
,
secondary heart field
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Fig. 2. Fgf is required for the patterning of late LPM markers. Hand1 (A and B) and foxf1 (C and D) are normally restricted in the anterior and middle LPM with a clear domain free of expression in both cases. When embryos are treated with SU5402, both hand1 (B) and foxf1 (D) are expressed along the entire anterior–posterior axis. Conversely, the LPM expression domains of both hoxc10 (E and F; normally expressed in the posterior half of the LPM) and tnni3 (G and H; marker of cardiac differentiation) are completely undetectable when Fgf signalling is inhibited. (A–F): lateral view of the embryos is shown, with anterior toward the left, dorsal at top. (G–H); ventral view of the heart region is shown, with anterior toward left. The total number of embryos examined for each panel is indicated in the lower left hand corner.
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Fig. 6. The extent of the vascular plexus is related to the size of the hand1 domain. To more directly assess the relationship between the forming vasculature and hand1 expression double in situ hybridizations were done with hand1 being visualized in light blue and etv2, marking the forming vasculature, in purple. The forming vascular plexus (emphasized in the lower panels of each example) along the side of the embryo does not extend to the end of the embryo in control (DMSO, ATP) embryos nor does the hand1 staining. When the extent of the vascular plexus is shifted towards the anterior end by treatment with RAA (A and D) this is reflected in the changes to the hand1 expression domain. When the vascular plexus is shifted towards the end of the embryo by addition of RA (C and F) or SU5402 (H and J) this is again reflected in the changes to the extent of hand1 expression domain along the anterior–posterior axis. Note that the close correspondence appears to be lost in the dorsal ventral axis in the SU5402-treated embryos (H and J). |
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hand1 (heart and neural crest derivatives expressed 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior left, dorsal up.
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