Fig. 4. Downregulation of Vg1 RBP does not affect roof plate and neural crest cell determination. Xpax3 mRNA expression was assayed by in situ hybridization, in embryos injected with either CMO (A,B) or AMO (C,D). Dorsal view of a CMO- (A) and AMO- (C) injected embryos at stage 14 showing expression of Xpax3 in the lateral domains of the neural plate. Following neural fold fusion, in CMO-injected embryos (B), roof-plate cells normally reach the midline and Xpax3 expression is observed in the dorsal aspect of the tube (arrows). In AMO-injected embryos (D), roof plate cells fail to migrate medially, and a groove devoid of Xpax3 expression is observed along the dorsal midline (arrows). Xsnail expression was also analyzed in CMO- (E-G) and AMO- (H-J) injected embryos. In stage 18 embryos, immediately preceding neural fold fusion, expression of Xsnail is not reduced, and in fact is somewhat enhanced, by AMO injection (H) when compared with embryos injected with CMO (E). After neural fold fusion, Xsnail-expressing cells are observed along the dorsal midline (arrows) in the CMO-injected embryos (F). In AMO-injected embryos at the same stage (stage 20; I), however, Xsnail expression is absent from the dorsal midline and instead is observed flanking the midline on either side (arrows). In stage 35 embryos injected with CMO, cells continue to express Xsnail in the branchial arches and throughout the head region (G), whereas no expression of Xsnail is detected anywhere in AMO-injected embryos at the same stage (J). (K,L) Xtwist expression in injected embryos. As seen with Xsnail, a dramatic reduction in the expression of the cranial neural crest marker Xtwist is observed in stage 30 embryos injected with AMO (L) when compared with the sibling CMO-injected (K) embryos. A-F,H,I are dorsal views; G,J,K,L are lateral views.