Figure 2. The phenotypes of the PCP gene mutants. A–G′, The structure of the MB in wild type (A, A′, F, F′), fzH51/fzD21 (B, B′), stbmstbm-6/stbmA3 (C, C′), and dsh1/Y (D, D′, E, E′, G, G′) mutants. The vertical or medial lobes were lost or reduced in the PCP mutants (B–D′, arrowheads). Anterior (A–E′) and dorsal views with the posterior side up and the anterior side down (F–G′) are indicated. In dsh1 mutants, a loss or reduction of the lobes (D, D′, arrowheads) or an aggregation of axons beside the calyx (E, E′, G, G′, arrow) was observed. In the case of axon aggregation, only a small portion of the γ neurons projected toward the anterior side (E, E′, G, G′, yellow arrowhead). The MB was visualized by the expression of GFP driven by OK107-Gal4 (green) and the γ and α/β lobes were visualized by anti-FasII antibody (magenta). H–O‴, The axonal projections of α/β KCs marked by GFP (H–O, O″, green; H′–O′, O‴, white) in wild type (FRT 19A control clone in H, H′; FRT G13 control clone in M, M′), fzH51/fzD21 mutants (I–J′), stbmstbm-6/stbmA3 mutants (K–L′), and dsh1 mutants (N–O‴). The axon bifurcated into both the vertical and the medial lobes in the wild type (H, H′, M, M′). The projection of sister branches in the same direction (I, I′, arrowheads), the stalling of the branched axon (K, K′, arrowhead), and the reversed projection of the branched axon into the peduncle (N, N′, arrowhead) are shown as examples of guidance defects. The absence of branches (J, J′, L, L′, O–O‴, arrowhead) is shown as an example of branching defects. In O–O‴, an ectopic branch at the peduncle projected in the posterior direction (arrow). O″ and O‴ are the dorsal views of O and O′, respectively. The asterisks in J and J′ indicate an axon of a clone induced in the contralateral MB. P–R, Genetic interaction between the PCP genes. Double heterozygotes of the stbmA3 and fzH51 (P), dsh1 and fzH51 (Q), or dsh1 and stbmA3 (R) showed a higher percentage of defects in the MB than single heterozygotes of fzH51, stbmA3, and dsh1 (***p < 0.001, **p < 0.01, Fisher's exact test).