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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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