Development of the dorsal neuraxis and some derivatives. Prior to 24 h, aln mutant embryos were identified by simultaneous staining for trp-2 expression, which is greatly reduced in the mutant retina (A–D). (A, B) Expression of pax-3 in the dorsal one-third of the neural keel in WT sibling (A) and aln mutant (B) 18.5-h embryos, double stained with trp-2 (indicated in A). (C, D) Expression of wnt-1 at the dorsal midline of the neural keel in WT sibling (C) and aln mutant (D) 18-h embryos, double stained with trp-2 (indicated in C). (E, F) Expression of wnt-3A in WT sibling (E) and aln mutant (F) 24-h embryos. A–F indicate that several markers of dorsal neural tube identity are reduced in expression level in aln mutants. (G, H) isl-1 expression in dorsal spinal cord marks Rohon-Beard primary sensory neurons in WT sibling (G) and aln mutant (H) 24-h embryos, shown in dorsal view with anterior to the left. (I, J) WT (I) and mutant (J) 24-h embryos exhibit similar patterns of c-ret expression in cranial neural crest derivatives, shown in dorsal three focal plane composite views with anterior to the left. The trigeminal (tg), anterior lateral line (all), and posterior lateral line (pll) ganglia as well as the vagal neural crest-derived precursors of the enteric nervous system (enp) are detected in aln mutants. (K, L) Precursors of craniofacial cartilage, marked by goosecoid expression at 42 h, are present in abnormally small patches in mutant embryos (L), compared to similarly staged albino embryos (K). (M) DiI-labeled neural crest cells (red) in the branchial arch region of a 48-h mutant embryo. DiI was applied to the neural fold at the one- to two- somite stage and the embryo was imaged under two-color confocal microscopy using a Bodipy (green) counterstain.
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