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Fig. 7. wt1, foxc2 and NICD are sufficient to activate podocyte gene expression. (A-B′) Transverse sections of whole-mount in situ hybridizations comparing kirrel (A,A′) and nphs1 (B,B′) expression in wt1* plus foxc2* mRNA-injected Xenopus embryos (A′,B′) and uninjected sibling controls (A,B) at stage 35. Injected and uninjected sides are indicated. (C) RT-PCR analysis comparing the expression of podocyte terminal differentiation genes nphs1, kirrel, ptpru and nphs2 and the transcription factors wt1 and foxc2 in uninjected whole embryos (WE control, lane 1), uninjected ventral marginal zone explants (VMZ control, lane 2) or ventral marginal zones injected with wt1* plus foxc2* mRNA (VMZ wt1*/foxc2*, lane 3), with NICD mRNA (VMZ NICD, lane 4), or co-injected with NICD, wt1* and foxc2* mRNA (VMZ NICD/wt1*/foxc2*, lane 5). (D,D′) Whole-mount in situ hybridization of control embryos (D) and embryos co-injected with NICD, wt1* and foxc2* mRNA (D′) for nphs1 expression at stage 35. Arrow indicates an ectopic patch of nphs1 expression. (E) Quantification of ectopic nphs1 patches in embryos injected with wt1*/foxc2*, NICD, wt1*/NICD, foxc2*/NICD and wt1*/foxc2*/NICD mRNA. (F) Schematic of Xenopus glomus development. The three transcription factors, wt1, foxc2 and hey1, activate the PGRN (podocyte gene regulatory network). Subsequently, differentiated podocytes secrete Vegf to recruit endothelial cells and mesangial cells to form the differentiated glomus (see Discussion for further details). |
