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Fig. 4 Effects of Pou5f3-ERT2 activation on the expression of genes regulating posterior development. (A) Schematic view of the Pou5f3-ERT2 fusion gene that was incorporated into pCS2+ and transcribed in vitro for mRNA microinjection. (B) Time schedule of Pou5f3-ERT2 activation by 4-OHT treatment. mRNA of 400 pg was injected into each fertilized egg, which was raised, administered with 5 μM 4-OHT at 18 hpf, and subjected to expression analyses at 20 hpf (C–P). (C–L) The expression of tail bud-related genes was examined by WISH. Up-regulation is marked with solid arrowheads. (M–P) Expression of tbxta and sox3 was stained in green and magenta, respectively, by FISH. Brackets mark the tail bud region. (Q–U) Effects of tbxta overexpression on the expression of tail bud-related genes. mRNA for egfp or tbxta was injected into embryos (100 pg/embryo), which were examined for the expression of tail bud-related genes at early somite stages. Down-regulation is marked with open arrowheads. Percentages of embryos with the shown patterns and total embryo numbers are shown in the right-bottom. For abbreviations, see the legend in Figure 2. WISH, whole-mount in situ hybridization. Scale bars, 200 μm.