unfX1/unfZ0001 compound heterozygotes display a range of aberrant mushroom body phenotypes, suggesting that unfX1 and unfZ0001 alleles interact. OK107-GAL4 was used to drive expression of the UAS-mCD8GFP transgene in all MB neurons and their axons (green), and anti-Fas II (red) to label the α and β axons. (A) In this unfX1/unfZ0001 compound heterozygote all MB axons stall (arrows), similar to the unfX1 mutant phenotype. (B) In this unfX1/unfZ0001 heterozygote only medial lobes are present, similar to the unfZ0001 mutant phenotype; a thin fascicle of α' axons is present in the right hemisphere (star). (C) In this unfX1/unfZ0001 heterozygote, left hemisphere β' and β axons extend medially beyond the midline (arrow), whereas γ axons appear to stall; right hemisphere β and β' axons misproject ventrally (arrowhead) and γ axons are highly disorganized; only a few α' dorsal axon projections are present in either hemisphere (stars). (D) In this unfX1/unfZ0001 heterozygote α and α' dorsal axon projections are present in the left hemisphere, whereas only a thin fascicle of α' axons is present in the right hemisphere (star); β axons are present in the right hemisphere and appear to stall (arrow), whereas they are completely absent in the left hemisphere. (E) In this unfX1/unfZ0001 heterozygote β', β, and γ axons project medially and cross the midline (arrow), but dorsal axons are missing in the left hemisphere; in the right hemisphere γ axons project medially and α and α' axons project dorsally but appear to stall (arrowhead). (F) In this unfX1/unfZ0001 heterozygote, α and α' dorsal axon projections are present in the left hemisphere, whereas only α' dorsal axons are present in the right hemisphere; medial axon projections are disorganized and stall before reaching the midline in both right and left hemispheres (arrows). Eb, ellipsoid body; Meb, median bundle; Ped, peduncle. Scale bars = 25 μm.