Fig. 2. Lithium-mediated inhibition of GSK3ß in late blastula shows involvement in ventrolateral-promoting Wnt signalling. Xenopus embryos analysed for marker gene expression with whole-mount RNA in situ hybridisation carried out at stage 11. Control embryos (A-D) were treated with NaCl and experimental embryos (E-H) were treated with LiCl at stage 9.5. In all embryos dorsal is towards the top. Control embryos (A-D) show normal molecular marker expression. The molecular markers used were chordin (Chd) and Xnot, which are dorsal specific, and XmyoD and Xpo, which mark ventral and lateral. Chordin acts as a control as it has previously been shown that it is unaffected by late blastula Wnt signalling. The expression of chordin therefore remains unchanged in the dorsal side of the embryo by lithium treatment (compare E with A). The expression of the dorsal marker Xnot is greatly reduced after inhibition of GSK3ß by lithium (F) when compared with the control embryo (B). Expression of the ventral and lateral markers XmyoD (G) and Xpo (H) are expanded into the dorsal midline of the embryo after lithium treatment whereas in control embryos (C,D) no expression is seen in the dorsal midline.