Fig. 1. MB defects in the drl LOF mutants are already present in newly hatched Drosophila first instar larvae and persist through metamorphosis. MBs are visualized in GAL4-OK107 UAS-mCD8-GFP individuals. (A,B,C) Wild-type brains, (D,E,F) drl LOF brains. Asterisks indicate the vertical lobes either present in the wild-type situation or reduced in the mutant situation. The midline is shown by a dashed line. The midline crossing is displayed at all stages in drl LOF mutant brains. In the displayed sample, the drl LOF mutant adult brain shows a disappearance of the ' vertical lobes (compare A with D). In late drl LOF mutant third instar larvae, the MB vertical larval lobes are absent in most of the analyzed brains (12 out of 15) (compare B with E). Much less reduction of the MB vertical larval lobes was observed in newly hatched first instar larvae (compare C with F). Scale bars: 50 µm in A and B; 20 µm in C.