Fig. 8. Quantitative RT-PCR analyses. To determine the effects of XSOX3 expression on endogenous genes, fertilized eggs were injected with wild-type or m8 XSOX3 RNAs (1 ng), and allowed to develop to stage 9, when they were homogenized and RNA was isolated and subjected to quantitative RT-PCR analysis. Compared with uninjected (un) and m8 (m8) injected controls, injection of wild-type XSOX3 RNA (wt) led to a decrease in the level of Xnr5 (A), Xnr6 (B), Siamois (C), Twin (D), Xnr3 (E) and Xbra (F) mRNAs. (G) The HMG boxes of XSOX3 and XSOXD differ at several positions [conservative changes are marked with an asterisk (*)]. (H) Compared with the ventralization of embryos following the injection of wild-type XSOX3 RNA (SOX3), injection of 650 pg mRNA encoding XSOXD-V5H₆ (SOXD) failed to ventralize embryos [uninjected embryos (un)]; immunocytochemistry revealed that the XSOXD-V5H₆ polypeptide had accumulated (data not shown). (I) Fertilized eggs were injected with 1 ng of either XSOX3-V5H₆ wild-type (wt) or XSOXD-V5H₆ RNA. At stage 9, embryos were homogenized and subjected to quantitative RT-PCR analysis. Injection of SOXD-V5H₆ RNA had no apparent effect on Xnr5 RNA levels.