Fig. 6. Analysis of the Xenopus hhex promoter. (A,B) Confocal analysis of bisected hhex:gfp transgenic embryos at (A) midgastrula and (B) early somite stages (anterior left), showing GFP (green) in the anterior endoderm. Embryos were counterstained with anti-ß-catenin antibodies (red). (C-E) 50% of the foregut explants (AEM) isolated from embryos with a heterozygous hhex:gfp transgenic father were GFP-positive as expected (C), whereas posterior explants (PEM) did not express GFP (D). By contrast, 4 of 12 posterior explants isolated from sibling embryos injected with Gsk3ß RNA (500 pg) were GFP-positive (E). Upper panels, bright field images; bottom panels, GFP. (F) The indicated hhex:luciferase constructs were injected into D1 or D4 cells at the 32-cell stage and luciferase activity was assayed at the gastrula stage. (G) Bar chart showing results of F as normalized relative luciferase activity.