Fig. 1. lola limits midline crossing of CNS axons. Wild-type (A) and lola mutant (B,D-F) stage 16/17 embryos were fixed, stained with anti-Fasciclin II (mAb1D4) and visualized by peroxidase histochemistry. (C) A robo^z14 embryo of the same stage is shown for comparison. Note multiple crossings of the CNS midline (arrows) by immunoreactive nerve tracts in all mutant panels, but not in the wild type. Midline is indicated by white triangle. (B) lola^1A4; (C) robo^z14; (D) lola^cn03089; (E) lola^ORB40; (F) lola^ORE76. (B,D,E) Hypomorphic lola alleles; (F) A strong/null lola mutant. Note reduction of longitudinal axon tracts in hypomorphic lola alleles and nearly complete absence in the strong allele. Anterior is towards the top in all panels.