Figure 1.
The sparse driver system and its demonstration in the Drosophila olfactory circuit
(A) The sparse driver system allows simultaneous expression of multiple transgenes in a subset of cells through stochastic TF (transcription factors) expression. The TF expression is gated by a pair of mutant FRTs (FRT10 or FRT100 sites) and a transcription termination sequence (shown as STOP). Heat-shock-induced stochastic FLP expression removes the STOP and enables TF expression in a fraction of cells, driving the co-expression of multiple genes of interest (GOI) in these cells.
(B) Adult Drosophila brain schematic highlighting antennal lobes and locations of the DA1 glomerulus. Left, DA1-ORN axons (green) synapse with DA1-PN dendrites (purple, contralateral projection omitted).
(C) Point mutations (the A→T mutation of FRT10 or the C→G mutation of FRT100) in the FRT-STOP-FRT sequence can reduce FLP-FRT recombination efficiency by approximately 10- or 100-fold, respectively. Following recombination, the in-frame peptide derived from the mutant FRT and T2A sequences is excised during the translation of the TF.
(D) A conventional split GAL4 strategy to target DA1-ORNs in the adult or pupal antennal lobe.
(E) The SparseFRT100-AD-based split GAL4 enables different sparsity tuned by heat-shock time (from 0 to 120 min).
(F) The SparseFRT10-AD-based split GAL4 enables different sparsity tuned by heat-shock time (from 0 to 5 min).
(G) Two procedures for sparse driver activation.