Fig. 3. XTcf3^– embryos express higher levels of dorso-anterior marker genes. (A) Uninjected (U), XTcf3^– embryos (2.5 ng, 3 ng or 3.5 ng T1 oligo) or XTcf3-embryos injected with 100 pg XTcf3 RNA (3.5 + mRNA) were collected throughout gastrulation (stages 9.5-11) and were analyzed by real-time RT-PCR. All samples in A were from a single host-transfer experiment. Relative expression levels for each gene were determined by comparison to a standard curve generated by serial dilution (100%-10%) of uninjected stage 10 controls. Expression levels of all genes were normalized to the level of ornithine decarboxylase prior to quantitation (not shown). Expression of early dorsal genes (siamois, Xnr3, chordin, goosecoid, Xnr6 and cerberus) were increased in XTcf3^– embryos and rescued (with the exception of Xnr6) by injection of XTcf3 RNA (3.5 + mRNA). (B) Uninjected (Un) or XTcf3^– embryos (Tcf3^–, 4 ng T1 oligo) were frozen at the tailbud stage (stage 32) for real-time RT-PCR as above. Stage-32 uninjected embryos were used for the standard curve. Late dorso-anterior genes Xlhbox8 and Nkx 2.3 were increased in XTcf3^– embryos. IFABP and -T4 globin were decreased in XTcf3^– embryos.