Fig. 1. Identification of l(X)MB342 based on presence of ectopic unrecognizable MARCM clones. (A) Composite confocal images of an adult brain showing labeling of the paired MBs by GAL4-OK107-driven expression of mCD8-GFP (arrows). GAL4-OK107 labels a few non-MB structures in the central brain (arrowheads). (B) Composite confocal images of a wild-type mosaic adult brain showing one MB Nb clone in the left hemisphere and multiple single-cell/two-cell clones of MB neurons in the right hemisphere. (C) Summary of the genetic crosses for the MARCM-based genetic screen. The star represents a mutagenized chromosome. (D) Composite confocal images of a mosaic adult brain containing clones of l(X)MB342 homozygous mutant neurons. Multiple ectopic clones with rudimentary projections are present. Clones were induced in newly hatched larvae unless otherwise indicated. Scale bar: 20 µm. Genotypes: (A) UAS-mCD8-GFP/+;GAL4-OK107/+; (B) FRT19A/FRT19A,hs-FLP,tubP-GAL80;UAS-mCD8-GFP/+;GAL4-OK107/+; and (D) FRT19A,l(X)MB342/FRT19A,hs-FLP,tubP-GAL80;UAS-mCD8-GFP/+;GAL4-OK107/+.