Fig. 1. Bchs overexpression disrupts eye development and photoreceptor growth cone morphology. (A-C) Adult eyes. (A) Control (GMR-GAL4) eye has normal rows of ommatidia. (B) Overexpression of wild-type Bchs in the eye (GMR-GAL4;EP-bchs) produces a small eye lacking distinct ommatidia. (C) An early stop codon in the bchs⁵⁸ allele prevents the overexpression phenotype, despite the presence of the EP-bchs insertion in this allele (GMR-GAL4;bchs⁵⁸). (A'-C') Photoreceptor (R-cell) axons in larval brain, labeled with anti-Chaoptin. Subsets of R-cell axons enter via the optic stalk to terminate in the lamina and medulla, from which the indicated region is enlarged in A''-C''. Compared with control brains (A',A''), overexpression of wild-type Bchs (B',B'') does not disrupt axon pathfinding, but causes photoreceptor growth cones (arrowheads) to have larger central areas and appear less expanded than controls. This phenotype is also prevented by the stop codon in bchs⁵⁸ (C',C''). Scale bars: 100 µm in A-C; 10 µm elsewhere. la, lamina; me, medulla; os, optic stalk.