Figure 1.

unf is required for mushroom body lobe formation. In the adult brain, the mushroom body (MB) is a paired neuropil structure that comprises five axonal lobes, γ, α'/β', and α/β. Each neuron projects dendrites that contribute to a large dendritic field (calyx), and an axon that travels anteroventrally. MB axons fasciculate with other MB axons forming a peduncle (Ped) before projecting axons medially and dorsally. α' and α axons project dorsally, whereas γ, β', and β axons project medially, forming five distinctive lobes. To visualize the MB lobes, OK107-GAL4 was used to drive expression of the UAS-mCD8GFP transgene in all MB neurons (Kenyon cells) and their axons. Lobes were distinguished by using anti-Fasciclin II (anti-Fas II) to label α and β lobes and anti-Trio to label α', β', and γ lobes. (A) In adult UAS-mCD8GFP;;OK107-GAL4 control animals labeled with anti-Fas II (red), all MB lobes have formed. (B) In unf^X1 mutants, MB axons have formed a peduncle (arrowhead), but have spread out and stalled prior to lobe formation (arrow). (C) In unf^Z0001 mutants, γ, β', and β axons projected medially, but were disorganized. No dorsal lobes were formed (star). (D) This +/Df2426;UAS-unf^RNAi;OK107-GAL4 adult displayed dramatically reduced dorsal lobes in one brain hemisphere (arrow). (E, F) In unf^X1 and unf^Z0001 rescue animals, in which a wild-type unf trangene was expressed in all MB neurons in an otherwise mutant background, all MB lobes were present. It is interesting to note that in rescued flies, MB lobes may have fewer axons, and that some medially projecting axons have extended past the midline (E, arrow). Eb, ellipsoid body; Meb, median bundle; Ped, peduncle. Scale bars = 10 μm.