elav regulatory sequences drive expression of 'nlgSNTQF2', an engineered receptor that can be used to monitor synaptic contacts between neurons in vivo. The nlgSNTQF2 protein is a fusion of 1. a single-chain antibody domain (SCAD) that recognizes the extracellular domain of Mmus\Cd19, 2. N amino acid residues 1460-1767, encoding the NRR (Notch regulatory region, a fragment of the extracellular domain) and TMD (transmembrane domain), 3. the Tag:TS(Nlg2) tag (which results in the protein being targeted to postsynaptic sites) and 4. the QF2 driver. The coding sequence is also tagged at the C-terminal end with Tag:V5. When nlgSNTQF2 is expressed postsynaptically in one neuron type, and an appropriate ligand protein (containing the extracellular domain of Mmus\Cd19, the binding partner of SCAD) is expressed presynaptically on a neuron that forms a synaptic contact with the nlgSNTQF2-expressing neuron, then upon binding of nlgSNTQF2 and the Mmus\Cd19 fragment, components of the endogenous Notch/Delta signaling pathway cleave the N sequences in the NRR and TMD, releasing the QF2 driver, which can then enter the nucleus and activate transcription of a QUAS-driven construct.