Fig. 9. Overexpression of Xcyr61 blocks activin-induced convergent-extension movements but not mesoderm induction. Inhibition of Xcyr61 function does not inhibit extension. (A-D) Animal pole explants are shown at stage 17, when activin induced elongation (B) is most obvious. Injection of full-length Xcyr61 (500 pg; C), but not Xcyr61 (1,2,3; 500 pg; D), blocks elongation. Uninjected control animal caps are shown in (A). (E-J) Animal caps allowed to develop to the equivalent of stage 32 and analysed for expression of cardiac actin. (E) Control animal caps. (F) Animal caps derived from embryos injected with RNA encoding Xcyr61. (G) Animal caps derived from embryos injected with RNA encoding Xcyr61 (1,2,3). (H) Activin-treated animal caps. (I) Activin-treated animal caps derived from embryos injected with RNA encoding Xcyr61. (J) Activin-treated animal caps derived from embryos injected with RNA encoding Xcyr61 (1,2,3). Note that Xcyr61 constructs do not inhibit induction of muscle by activin. (K-M) Inhibition of Xcyr61 function does not inhibit activin-induced elongation of isolated animal pole regions. (K) Control animal caps: no elongation occurs. (L) Activin-treated animal caps elongate. (M) Animal caps derived from embryos previously injected with antisense morpholino oligonucleotide MO3 undergo elongation. Elongation of such animal caps appears to be more extensive than is observed in control animal pole regions.