Larger Image Fig. 5. Fgf and RA signalling are required for proper patterning of the trunk vascular system. Embryos were treated with DMSO or SU5402 at stage 12 (top panel: AH) and allowed to develop until stage 32 at which point vascular pattern was assessed by expression of etv2 (AD) and aplnr (EH). Both etv2 (A and B) and aplnr (E and F) are normally restricted from the posterior end of the LPM. However, when Fgf signalling is lost, the expression domains of both etv2 (C and D) and aplnr (G and H) are extended posterior to the end of the trunk. Also, the anterior gap in vasculature between the rostral lymph sac and trunk vasculature, corresponding to the location of developing heart, is absent in SU5402 treated embryos. Embryos treated at stage 14 with a synthetic RA antagonist (RAA), all-trans RA or a DMSO control (bottom panel: IT) were assayed for etv2 (AF) or aplnr (GL) expression. While no obvious changes are present after treating embryos with RAA (I,J and O,P), the posterior limit of the LPM vasculature (white arrowheads) is extended further posterior in RA treated embryos (M,N and S,T) when compared with control embryos (K,L and Q,R). The staining seen in the rostral lymph sac is also absent in embryos treated with RA. White arrows: posterior limit of trunk vascular pattern. Red arrows: rostral lymph sac. Black arrows: gap between rostral lymph sac and trunk vasculature. The total number of embryos examined for each panel is indicated in the lower left hand corner. Image published in: Deimling SJ and Drysdale TA (2011) Copyright © 2011. Image reproduced with permission of the Publisher, Elsevier B. V.
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