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Fig. 3 Tissue-specific ERT2-GAL4 produces 4-OHT-dependent, region restricted activity of transgene expression. (A-E) Transient transgenics in which ERT2-GAL4 is under control of the HuC enhancer/promoter show robust neuron-specific expression from co-injected UAS::H2B-citrine when embryos are treated overnight with 0.5 μM 4-OHT, compared with controls (compare B-E versus A, green channel). Staining with anti-HuC/D antibody reveals the endogenous expression pattern of this gene (A-E, red channel). Images in A-C are maximum projections of the entire embryo thickness (36-40 μm). Images in D,E are enlarged maximum projections of a 5.7 μm stack from embryo in C. (F-M) Stable transgenics in which cldnB enhancer/promoter drives ERT2-GAL4 show robust induction and 4-OHT dependence of a stable 5×UAS::H2B-citrine transgene (compare J,K,L versus F,G,H, green channel). When treated with 1 μM 4-OHT from 50% epiboly, embryos express Citrine in the migrating lateral line primordium and deposit neuromasts at 30 hpf (dotted ovals in K and J, respectively, green channel). Persistent expression of the UAS-linked citrine at 48 hpf in neuromasts is detected by in situ hybridisation for citrine transcript (compare M with I, red circled purple signal). Some samples were co-stained with DAPI to reveal nuclei (F-H,J-L, red channel). Additional Citrine-positive cells outside the lateral line structures in J-L reflect the expression of Cldnb in the skin.