FIG. 3. Core splitting and branching defects in Ptp10D mutants.

Third instar larval brains (A–F) and adult brains (N–P), showing morphologies of MB lobes visualized with anti-Fas II. Reconstructions of optical sections are shown. (A) Wild-type control. (B) ML fusion and branching defect, in a Δ59 hemizygote. The MLs from the two hemispheres are fused at the midline (arrowhead). The dorsal lobe in the right hemisphere is very thin (open arrowhead). (C) A Ptp10D¹ MB with a branching defect, showing a thin dorsal lobe in the right hemisphere (open arrowhead). (D) MB from a Ptp10D¹/Δ59 transheterozygote, showing an ML fusion (arrowhead). (E) bif^R47/Δ59, also showing ML fusion (arrowhead). (F) Δ59 with UAS-Bif driven by OK107. The ML is very thin (arrowhead). (G–L) Single optical sections through the peduncle, showing core fiber bundles labeled with phalloidin (magenta) and Fas II expression on surrounding axons (green). (G) Wild-type control. Note the single magenta spot within the green peduncle tract. (H) Core defect, in a Δ59 MB. Three distinct magenta core fiber bundles are observed (arrowheads). (I–L) Normal peduncles, in four different genotypes. (M) Bar graph showing phenotypic penetrances in Ptp10D and bif mutants, mutant combinations, and rescued genotypes. Note that the bar height for ML fusion indicates the % of brains affected, while those for other phenotypes indicate the % of MBs affected. (N) Wild-type control brain. The α, β, and γ lobes, which express FasII, are indicated. All wild-type MBs (30/30 brains) had this morphology. (O) 26/28 Ptp99A¹/Df(3R)R3 brains had normal MB morphologies. (P) 2/28 Ptp99A¹/Df(3R)R3 brains had an MB with a branching defect in which the α lobe is missing and the β lobe is enlarged. Bar in (A), 20 μm: applies also to (B–F); bar in (G), 10 μm: applies also to (H–L); bar in (N), 20 μm: applies also to (O and P).