Fig. 6. Commissure formation requires endocytosis. 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. (B) Overexpression of schizo in all midline cells of a heterozygous slit embryo leads to a fused commissure phenotype. (C) Expression of a dominant negative form of Shibire in all CNS midline cells blocks endocytosis and leads to a schizo-like CNS phenotype. (D) Expression of a dominant negative form of Shibire in all CNS midline cells of a heterozygous slit animal does not impair commissure formation. (E) Expression of a dominant negative Arf6 protein in all CNS midline cells lead to schizo phenocopy.