Fig. 1.
RABV-mediated tracing of synapses onto adult-generated neurons in the DG. (A) Retroviral and RABV constructs. (B) Scheme of sequential virus delivery. (C) Implementation of the method in the DG of the hippocampus. Proliferating neural progenitors in the adult SGZ are transduced with the retrovirus, thus rendering them infectable by the RABV and their neuronal progeny capable of transsynaptic RABV transfer, followed by a second injection of RABV. Once synaptogenesis has taken place, RABV spreads from the primary infected neurons to their presynaptic partners. (D) Injection scheme used in the DG. Representative examples demonstrating the specificity of the system. Reconstructed confocal images from multiple fields depict cells labeled after injecting G and TVA encoding retrovirus in runner and nonrunner mice or control DsRed-only retrovirus, followed by RABV injection. White arrowheads: double transduced newborn neurons. (Scale bar, 50 μm.) (E) Absolute number of double-transduced starter neurons per mouse and ratio of RABV-traced local presynaptic neurons versus double-transduced neurons in running mice compared with nonrunners (n = at least three mice per condition; *P < 0.05).