Fig. 1. MOs against Tcf/Lef factors produce different and specific phenotypes. (A) XlTcf1, XlLef1 or XlTcf3 MOs specifically inhibit protein synthesis from its corresponding DNA construct in in-vitro transcription and translation assays, while not affecting significantly translation of other Tcf constructs or a control luciferase DNA construct. Injection of 60 ng control MO into LMZs of both blastomeres at the 2-cell stage, or the marginal zones of two dorsal blastomeres (DMZ) or two ventral blastomeres (VMZ) does not affect the phenotype significantly (B,C,D). Injection of 20 ng Tcf1 MO into the LMZ causes a severe developmental arrest phenotype in the majority of embryos, and in the rest (E) or when only 15 ng Tcf1 MO is injected it interferes with both dorsal and ventral development (S). Injection of 20 or 15 ng of Tcf1 MO into the DMZ causes a severe dorsal bend at approximately the position of hindbrain (F,S), and into the VMZ causes an anteriorized phenotype (G,S). Injection of 60 ng Lef1 MO into the LMZ interferes slightly with both dorsal and ventral development (H,S), into the DMZ causes a slight dorsal bend (I,S), and into the VMZ causes a mild defect in ventral tissue development and a significant defect of tail development (J,S). Injection of 60 ng Tcf3 MO into the LMZ interferes with both dorsal and ventral development (K,S), but to a lesser degree than 20 or 15 ng of Tcf1 MO does. Injection of 60 ng Tcf3 MO into the DMZ causes a complete headless phenotype (L,S), and into the VMZ causes significant ventral development defects in both anterior and posterior regions (M,S). (N-R) Vegetal view of chordin (Xchd) expression in stage 10.5 embryos, dorsal towards the top, injections into the right side. The expression pattern and level of Xchd are not significantly affected by injection of 60 ng control MO (N), 20 ng Tcf1 MO (O), 60 ng Lef1 MO (P), 60 ng Tcf3 MO (Q) or 60 ng Tcf4 MO (R). (S) Numerical summary illustrating penetrance of morphological phenotypes caused by Tcf/Lef MOs, indicating dorsoanterior defects (i.e. clearly identifiable defects in the dorsal axis and the head and neck region), ventrolateral defects and combinations of these defects (but note that the detailed nature and severity of defects vary between Tcf1 MO, Lef1 MO and Tcf3 MO experiments, as illustrated in panels B-M).