Fig. 3. Zic2 regulates Xnr expression during gastrulation. (A) Dose-dependent induction of Xnr5 by injected tZic2 RNA (330 pg, 660 pg, 990 pg) in whole embryos assayed by real-time RT-PCR. Un, uninjected embryo. (B) Expression of Xnrs, mesoderm and endoderm markers in control (Un) and Zic2-depleted (Zic2-; 5 ng oligo 10MP) embryos assayed by real-time RT-PCR at stage 10.25 (left panel) and stage 10.5 (right panel). (C) Increased activin-like activity in Zic2-depleted embryos. Mean relative luciferase units (RLU)=A3-luciferase activity (3x activin response element)/RLTK (Renilla luciferase, thymidine kinase promoter) activity. Error bars show s.d. in a representative experiment; the asterisk indicates statistical significance (P<0.05).