The P{trans-Tango} construct encodes a system that can be used for transsynaptic circuit tracing and/or manipulation in vivo. It encodes three components: 1. a pan-neuronally expressed fusion protein that consists of the Hsap\GCGR receptor fused via a Tag:CS(TEVp) cleavage site to the QF transcriptional activator (Hsap\GCGR^{nSyb.Tango.QF}), 2. a membrane-tethered form of the Hsap\GCG ligand (Hsap\GCG::Nrx-1::Hsap\ICAM1^UAS.Tag:MYC) that is expressed under the control of UAS regulatory sequences and is enriched in axon termini when expressed, 3. a pan-neuronally expressed fusion protein that consists of Hsap\ARRB2 fused to the TEVp protease (Hsap\ARRB2::TEV\NIa^elav.Tango). Expression of the Hsap\GCG::Nrx-1::Hsap\ICAM1^UAS.Tag:MYC ligand in neurons using an appropriate GAL4 driver results in the protein accumulating in the presynaptic terminals of these neurons, where the ligand can activate the Hsap\GCGR receptor only in the postsynaptic neuron. The activated receptor recruits the Hsap\ARRB2::TEV\NIa^elav.Tango fusion protein, which cleaves the Hsap\GCGR^{nSyb.Tango.QF} protein to release the QF driver, allowing it to translocate to the nucleus and activate transcription of a QUAS-controlled reporter or effector construct.

The nSyb promoter drives expression of a fusion protein that consists of the Hsap\GCGR gene fused via a Tag:CS(TEVp) cleavage site to the QF transcriptional activator. The presence of Hsap\GCGR tethers the fusion protein to the cell membrane. The QF driver can be released from the membrane by cleavage of the Tag:CS(TEVp) site with the TEVp protease.

UAS regulatory sequences drive expression of a membrane-tethered form of the Hsap\GCG ligand. The protein consists of Hsap\GCG, a flexible linker containing a Tag:MYC tag, the extracellular domain of Hsap\ICAM1, and the transmembrane and cytoplasmic domains of Nrx-1. The Hsap\GCG ligand sequence is a mutant form that has a high potency for activation of the Hsap\GCGR receptor. The protein is sized to extend across the average length of a synapse, is enriched in axons and is targeted to axon termini.

elav promoter sequences drive expression of a fusion protein that consists of Hsap\ARRB2 fused to the TEVp protease.