Fig. 1. Nervous system defects in SoxNeuro mutants. Flat preparations (A-E,G,H) or a whole-mount (F) of stage 16 (A,B,E-H) and stage 11 (C,D) wild-type (A,C,E,G) and SoxNeuro^U6–35 (B,D,F,H) embryos stained with anti-Eagle (blue) and anti-Engrailed (brown) (A,B), anti-Eagle (blue) and anti-Ems (brown) (C,D), monoclonal antibody mAbBP102 (E,F) and anti-Fasciclin II (G,H). (A,B) In wild-type embryos, Eagle staining is observed in progeny of the NB2-4, NB3-3, NB7-3 and thoracic NB6-4 lineages. In SoxNeuro^U6–35 embryos, no Eagle staining is seen in these lineages. Eagle expression is still seen in cells in the gnathal midline. (C,D) Ems-expressing progeny of the NB3-5 and NB4-4 and NB3-3 lineages are absent in more than 96% of hemisegments in SoxNeuro^U6–35 embryos. Note that in embryos in which one of these cells is observed, we are unable to unambiguously identify which of the three neuroblasts is present. Tracheal Ems expression is still present. (E,F) In SoxNeuro^U6–35 embryos, longitudinal BP102 staining is absent in 60% of hemisegments (arrowheads in F); in addition commissures fail to separate correctly in 52% of hemisegments. (G,H) In SoxNeuro^U6–35 embryos, the regular axonal fasciculation pattern is disrupted and many axons cross the midline inappropriately (arrow).