Fig. 6. Inhibition of neural crest migration in AMO-injected embryos is independent of neural tube closure. Two-cell stage embryos injected in both blastomeres with a low concentration (6.5 ng/blastomere) of AMO (B,D) were analyzed by confocal microscopy for neural crest cell migration and neural tube closure, when compared with uninjected controls (A,C). In stage 25 control embryos, neural crest cells (arrows) can be observed above the neural tube (A), but are completely absent in AMO-injected embryos (B). By stage 30, in control embryos (C), migrating neural crest cells move ventrally around the neural tube, as well as into the dorsal fin. In sibling, AMO-injected embryos (D), no migrating neural crest cells are detected. Note the completely sealed neural tube in the AMO-injected embryos; the neural tube is outlined in white. no, notochord.