FIG. 5. Lar MB phenotypes: medial lobe fusion and branching defects.

(A–D) Third instar larval brain hemispheres stained with anti-FasII to reveal MB morphologies. Reconstructions of optical sections are shown. Open arrowheads indicate dorsal lobes (DL); closed arrowheads indicate medial lobes (ML). (A) Wild-type control. (B) Lar^5.1/Lar^13.2 transheterozygote. One DL is thin and the other absent, and the MLs are fused across the midline. (C) Lar^5.5/Lar^13.2 transheterozygote. Same phenotype as in (B). (D) Lar^OD5/Lar^13.2 transheterozygote. Both DLs are absent and the MLs are fused. (E–I) MARCM NB clones (positively labeled with mCD8-GFP), examined at third-instar larval stage (E–F) or in adults (G–I). GFP signal is in green, and anti-FasII in magenta, in (E1) and (F1), which are higher-magnification views; (E) and (F) show the GFP signal alone, in white. The brain midline is indicated by a yellow vertical bar in (E) and (F). (E, E1): control clone, showing the calyx (CX), DL, and ML. Note that the end of the ML portion of the clone is to the left of the brain midline. (F,F1): Lar^5.5 clone. Note that the ML axons extend beyond the brain midline (arrowheads), and enter the contralateral ML lobe (arrowhead in F1). (G–I) Adult clones, visualized with mCD8-GFP (green) and anti-FasII (magenta). (G) Control clone. The α, α′, β, and γ lobes are indicated. (H) Lar^5.5 clone. Note that some β lobe axons (arrowhead) extend across the brain midline and contact the contralateral anti-FasII-stained β lobe. (I) Lar⁴⁵¹ clone. The α lobe portion of the clone is missing, and the β lobe is doubled in thickness (arrowhead), indicating a defect in branching. (J–K): single cell/two-cell MARCM clones, showing dendritic endings in the calyx. The dendrites end in “claw-like” terminals (arrowheads). (J) Control clone. (K) Lar^5.5 clone. No obvious difference in morphology of the dendritic endings is seen. (L) Bar graph of phenotypic penetrances in Lar mutant larvae. Note that the bar height for ML fusion indicates the % of brains affected, while those for other phenotypes indicate the % of MBs affected. (M) Bar graph of phenotypic penetrances in Lar mutant NB clones examined at the larval or adult stages. Bar in (A), 20 μm: applies also to (B–D); bar in (E), 20 μm: applies also to (F); bar in (E1), 20 μm: applies also to (F1) ; bar in (G), 20 μm: applies also to (H–I); bar in (J), 10 μm: applies also to (K).