Fig. 1. Brain atlas and mosaic analysis. (A) Schematic of the olfactory circuitry (left hemisphere) and brain structures (right hemisphere) in the adult Drosophila. The olfactory circuitry is exemplified by representative olfactory receptor neurons (green), antennal lobe neurons, which include projection neurons (blue) and interneurons (purple), and mushroom body neurons (orange). Various brain structures are outlined by solid or broken lines and are superimposed with different colors. The naming of brain structures follows Otsuna and Ito (Otsuna and Ito, 2006). Abbreviations: adPN, anterodorsal projection neuron; AN, antennal nerve; AL, antennal lobe; lPN, lateral projection neuron; LN, local interneuron; de, deutocerebrum other than the AL; GC, great commissure; LH, lateral horn; MB, mushroom body; MBN, mushroom body neuron; ORN, olfactory receptor neuron; pilpr, posterior inferior lateral protocerebrum; pimpr, posterior inferior medial protocerebrum; SOG, sub-esophageal ganglion; vlpr, ventrolateral protocerebrum. (B) The genetic basis of MARCM (top) and dual-expression-control MARCM (bottom). Mitotic recombination mediated by flipase (FLP) in the heterozygous mother cell leads to the loss of GAL80 in one of the two homozygous daughter cells. All GAL80-negative progenies are labeled by tubP-LG-driven lexop-rCD2::GFP (green outlined oval), and only GAL80-negative GAL4-positive cells are dually labeled by GAL4-controlled UAS-mCD8 (pink oval). (C) Clone size in dual-expression-control MARCM. The induction of multicellular Nb clone (green outlined circles in the upper panel) or single-cell clone (green outlined circle in the lower panel) depends on the occurrence of FLP-mediated mitotic recombination in the self-renewing progenitor or ganglion mother cell. Within the clone, only GAL4-positive cells can be labeled by GAL4 and LexA::GAD simultaneously (green outlined pink circles). Abbreviations: Nb, neuroblast; GMC, ganglion mother cell; N, neuron.