Enhancer trap expression of theamn^28A is widespread in the developing nervous system. Expression of the GAL4 yeast protein contained in the P-element insertion ofamn^28A mutants was visualized by GAL4-driven expression of UAS–GFP (green fluorescent protein [S65T]) in amn^28A;UAS–GFP/+ males oramn^28A/+;UAS–GFP/+ females. In addition, expression was visualized by GAL4-driven expression of UAS–lacZ inamn^28A;UAS–lacZ/+males oramn^28A/+;UAS–lacZ/+ females. A, GFP expression in adults was widespread throughout the central brain (CB) and, to a lesser extent, in the optic lobes (OL). B, GFP expression in the CNS of third instar larvae was widespread in the central brain (CB), ventral ganglion (VG), and, to a lesser extent, in the optic lobe anlagen (OA). C, GFP expression in the embryo was most apparent in non-neuronal tissue, such as the salivary glands (SG) and gut (which is common for many PGAL4 lines) and peripheral cells that appear to be neuronal. D–F, Whole-mount views of lacZimmunoreactivity in the embryo revealed expression in the ventral nerve cord (VNC; D, E), and PNS (D, F).