Fig. 3. schizo affects the balance between repulsive and attractive signaling. Frontal views of dissected central nervous system (CNS) preparations of stage-16 embryos stained for the presence of all CNS axons using Mab BP102. Anterior is up. (A) Wild-type embryo. Two commissures form in each neuromere. (B) schizo mutant embryo lacks many commissural tracts. (C) Expression of netrinB in all CNS midline cells of schizo mutant restores the commissural pattern. (D) Embryos homozygous for the hypomorphic slit⁵⁵⁰ allele develop a characteristic fused commissure phenotype, which is similar to the loss of function robo1 phenotype (E). (F,G) The schizo mutant phenotype is reverted by reducing the dose of slit or robo. (H) Overexpression of schizo using a translocation chromosome in a heterozygous slit mutant background also led to a fused commissure phenotype.