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Figure 10. Transcriptional regulation of X-TSK and model of X-TSK function in germ layer formation and patterning.(A) Semi-quantitative RT-PCR of X-TSK expression in animal caps injected with 1 ng XFD, 50 pg V-ras or 50 pg caFGFR. WE = Whole embryo, WOC = Water only control. Inhibition of FGF signals with XFD enhances TSK expression, whereas activation of FGF signals with V-ras or caFGFR reduces TSK expression levels. (B) Model of TSK function in Xenopus germ layer formation and patterning: dorsal-ventral mesoderm patterning. X-TSK in dorsal mesoderm (red) inhibits BMP signaling to promote dorsal mesoderm formation, as marked by Gsc expression. This is possibly also enhanced through activation of Xnr2 signals by TSK. MAPK activation inhibits X-TSK expression in ventrolateral mesoderm, where X-TSK inhibits expression of ventrolateral mesoderm markers such as Xbra, through inhibition of FGF signaling. This network of signaling may contribute to clear patterning of the mesoderm. (C) Model of TSK function in endoderm formation. X-TSK coordinates inhibition of FGF and BMP signals with activation of Xnr2 signaling to induce endoderm formation (green), as marked by Sox17α. Again, X-TSK inhibits expression of ventrolateral mesoderm (blue) markers such as Xbra, through inhibition of FGF signaling and may contribute to the distinction between endoderm and mesoderm specific gene expression. Image published in: Morris SA et al. (2007) Morris et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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