XB-IMG-23465
Xenbase Image ID: 23465
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Fig. 1. Pronephros development is sensitive to FGF overexpression, although pronephros precursors express Xbra. (A) Analysis of GFP distribution in transgenic Xbra-GFP embryos. Transverse sections of embryos at the late gastrula stage (NF st. 12.5), mid-neurula stage (NF st. 16) and tailbud stage (NF st. 25). GFP remains detectable long after the transgene has been switched off, i.e., by the end of gastrulation, allowing the identification of Xbra-expressing cells progeny. GFP is detected in the dorsal mesodermal structures, but is absent ventrally. There is no sharp limit between these two domains. Rather, cells expressing low levels of GFP are intercalated with negative cells in the lateral mesoderm. At the late gastrula stage and the mid-neurula stage, GFP is expressed in paraxial (pm) and laterodorsal mesoderm. At the tailbud stage, GFP is strongly detected in somites (s) and pronephros anlage (pa), but is absent from ventral blood islands (vbi). (n) notochord, (nt) neural tube. (B) In situ hybridization analysis of mesodermal markers in response to exogenous FGF4. Analyses of XmyoD, XPax-8 and Xlim-1 expression at the neurula stage, and SCL at the tailbud stage. FGF4 expression was targeted on the right side of the embryos (XmyoD, XPax-8, Xlim-1) or ventrally (SCL). In some cases, β-galactosidase was co-expressed with FGF4 and revealed with Red Gal. XmyoD expression is slightly expanded on the injected side. SCL expression is inhibited in response to exogenous FGF4. XPax-8 and Xlim-1 expression is totally abolished by FGF4 overexpression. (C) RT-PCR analysis of pronephros markers in combined marginal zone explants. Expression of XWT1 and XSMP30 is induced in VMZ explants combined with DMZ explants in response to signals from Spemann's organizer. FGF4 overexpression in VMZ causes a strong inhibition of XWT1 and XSMP30 expression. (D) Expression of a constitutive FGFR (t-R1) impedes mesodermal cells to adopt a pronephric fate. Small aggregates of control cells stained with RLDx and cells expressing t-R1 and GFP were implanted in the dorsolateral marginal zone of unlabelled recipient embryos, as described in Materials and methods. Distribution of fluorescent cells was analyzed at early tadpole stage. Both kinds of cells are able to differentiate into well elongated somitic cells. However, only control cells populate the pronephros. Image published in: Colas A et al. (2008) Copyright © 2008. Image reproduced with permission of the Publisher, Elsevier B. V.
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