Fig. 5. Regulation and function of Xenopus hhex. (A) Analysis of hhex expression by in situ hybridization to bisected stage-18 embryos (anterior left). (a) Schematic of a stage-18 bisected embryo showing the presumptive foregut (fg, green) and hindgut domain (hg). (b) Injection of GR-LEFN-ßCTA RNA (800 pg) into the D1 anterior endoderm cell has no effect without Dex. (c) Addition of Dex (1 µM) at the midgastrula repressed hhex expression as does (d) D1 injection of stabilized pt-ß-catenin RNA (250 pg). (e) Uninjected control embryo. (f) Injection of NTcf3 RNA (800 pg) or (g) Gsk3ß RNA (500 pg) in posterior D4 cells results in ectopic hhex expression (arrowhead). (h) Co-injection of Gsk3ß and ß-gal RNA reveals that the blue ß-gal stain co-localizes with ectopic hhex in the endoderm. (B) Hhex is required for liver and pancreas development. 32-cell stage embryos were injected with either an antisense hhex morpholino oligo (HexMO, 80 ng) in the D1 cells or with Gsk3ß or Gsk3ß plus HexMO in D4 cells. At stage 35, embryos were assayed by in situ hybridization with liver (for1) or pancreas/duodenum (pdx1) probes.