Fig. 6. Expressing a single Ncad isoform in R7s is sufficient to rescue Ncad mutant phenotypes. Single Ncad mutant R7 cells were generated using GMR-Flp-mediated mitotic recombination, and a single Ncad isoforms 7b-13a-18a (A,A',C,C') or 7b-13a-18b (B,B',D,D') was expressed in these mutant R7s. These R7 axons (green) were labeled using the MARCM system and mCD8-GFP to assess layer-selection at 17% APF (A-B'), and 35% APF (C-D'). As in the wild type, the MACRM-rescued R7 growth cones (arrows) project past the R8-temporary layer and expand their growth cones (double arrows) to terminate (arrowheads) at the R7-temporary layer (A',B') where they still remain at 35% APF (arrows in C',D'). R7 and R8 axons were visualized with Mab24B10 (red). The presumptive R7 and R8-temporary layers are indicated by dotted lines in (A',B'). (A'-D') High-magnification views of A-D, respectively. Scale bars: in A, 30 µm for A-D; in A', 10 µm for A'-D'. Abbreviations as in Fig. 1. (E) Table summarizing the observed R7 targeting defects in wild type, various mutant backgrounds, and transgene-rescues.