lexAop regulatory sequences drive expression of 'pre-mGRASP' tagged at the C-terminal end with 2xTag:HA followed by sequence encoding a portion of the cac gene. pre-mGRASP (PMID:22138823) is composed of an N-terminal signal peptide, the spGFP11 split fluorescent protein fragment, the extracellular and transmembrane domains of the human CD4 gene and an intracellular domain that targets the protein to presynaptic sites (Tag:TS(rNrxn1-β)). This construct is designed for use in the activity-independent t-GRASP (targeted GFP Reconstitution Across Synaptic Partners) assay, in which complementary split fluorescent protein fragments expressed on the extracellular surface of different neurons (the two components are targeted to pre-synaptic terminals and dendrites respectively) can reconstitute a functional fluorescent protein at points of synaptic contact between the neurons. Thus t-GRASP can be used to assess neural connectivity.