Fig. 3

Tail formation in the absence of nodal signalling. (A) A wild-type embryo. (B) An MZoep embryo, with an arrowhead highlighting somites within the tail region. (C,D) Embryos previously injected at the 128-cell stage with zebrafish bmp4 and wnt8 (50 pg of each). (C) Injection of bmp4 and wnt8 into wild-type embryos produced an ectopic tail (arrow) containing somites. Ectopic tails formed in 22% of injected embryos (n=117). Injection of Xenopus laevis BMP4 and Wnt8 induced ectopic tails in 18% of injected embryos (data not shown, n=114). (D) Injection of bmp4 and wnt8 into MZoep embryos led to the formation of an ecoptic tail (arrow) in 29% of injected embryos (n=29). A magnified image of the ectopic tail (inset), which was identified by co-injection of a marker (not shown), highlights somites within the tail (arrowhead).