(a) Animal explants dissected from embryos injected in one blastomere at the 2-cell stage with Zic1GR mRNA and cultured for 8 hours in dexamethasone, with or without the pharmacological inhibitors Disulfiram (100 μM), Citral (100 μM) or AGN193109 (10 μM). (b) RT-PCR analysis of Six1 and Eya1 expression in animal explants expressing Zic1GR treated with Disulfiram or Citral. Odc (Ornithine decarboxylase) is shown as a loading control. Controls are uninjected (Uninj) and GR mRNA injected (GR) animal explants. Similar results were obtained in four independent experiments for each inhibitor. The position of markers of known size is indicated (bp). (c) RT-PCR analysis of Six1 and Eya1 expression in Zic1GR injected animal explants treated with the pan-RAR antagonist, AGN193109. Controls are uninjected (Uninj), GR mRNA injected (GR) and Zic1GR mRNA injected treated with DMSO (+DMSO) animal explants. Similar results were obtained in six independent experiments. The position of markers of known size is indicated (bp). (d) AGN193109 treatment blocks Hnf1b expression in the posterior hindbrain (100% of the embryos; n=94), while in DMSO-treated embryos Hnf1b expression is similar to that of control embryos (100% of the embryos; n=52 and n=37, respectively). Three independent experiments were performed. Stage 13 embryos, dorsal views, anterior to top. Scale bars, 200 μm.