Defects of neural tube and motoneuron formation in <i>dlx5a/6a</i> zebrafish morphants.

(A-F) Lateral views of whole-mount in situ hybridization for foxd3, ncad and msx1b in controls and dlx5a/6a zebrafish morphants at 24 hpf (n>8 for each condition). (A’-D’) In situ hybridization for foxd3 and ncad on coronal cryosections at levels indicated by lines in (A-D). The dlx5a/6a morphants show a reduced neural tube (A’-D’) associated with a defect of NCC migration (B’, black arrowhead), aberrant accumulation of foxd3 and ncad transcripts in somites (B, D) and decrease of msx1b in the neural tube (F, black arrowhead). (G-L) Lateral views of whole-mount immunostaining for SV2 in 24 hpf, 30 hpf and 36 hpf control and dlx5a/6a morphant embryos (n>8 for each condition). In dlx5a/6a morphants at 24 hpf and 30 hpf, axonal projections of primary motoneurons fail to form (H-J). In 36 hpf morphants, primary motoneurons show abnormal synaptic connections to their myotomal targets (L). Abbreviations: mff, median fin fold; my, myotomes; nc, notochord; ncc, neural crest cells; nt, neural tube; pmn, primary motoneurons; psm, presomitic mesoderm; sm; somitic mesoderm, ys, yolk sac. Scale bar in A for A-F 100 μm, for A’-D’ 25 μm and for G-L 50 μm.