prdm1 mRNA injection can rescue Rohon–Beard sensory neurons and neural crest cells in nrd mutant embryos. HNK-1 immunohistochemistry, dorsolateral views; anterior is to the left. (A) Expression pattern of HNK-1 in RB sensory neurons in a wildtype embryo. (C) nrdm805 embryos lack RB sensory neurons and do not express HNK-1 in the dorsal neural tube. (E) RB sensory neurons are induced to form in nrdm805 mutant embryos after injection of prdm1 mRNA (arrows point to several RB sensory neurons). Crestin expression in lateral views, anterior to the left. (B) Wildtype expression of crestin at 24 hpf. (D) nrd embryos have very little trunk neural crest migration (F) After injection of prdm1 mRNA, numerous crestin-positive neural crest cells can be seen in the migration pathway (arrows). Abbreviations: wt, wildtype; nrd, narrowminded mutant embryos. Scale bar is 50 μm.