Fig. 1

The structures of all viral tracers used in our study. (a) Structures of multi-trans-synaptic retrograde viruses including RV-B2C-EGFP and PRV-152 are illustrated. For RV-B2C-EGFP, EGFP gene was inserted between G- and L-coding sequences of CVS-B2C strain. For PRV-152, EGFP was driven by the CMV promoter following gG gene of the Bartha strain. (b) Structures of mono-synaptic retrograde viruses are illustrated. Because TK (thymidine kinase) gene is involved in viral replication and US9 is responsible for anterograde transport, a retrograde mono-synaptic tracing virus PRV-∆TK-∆US9-EGFP was obtained by deleting both TK and US9 genes, in which the location of US9 gene was replaced by CMV promoter and EGFP gene via homologous recombination on the BAC backbone of the Becker strain. For the RV-∆G mono-synaptic virus, EGFP, DsRed and Cre-T2A-tagBFP was respectively inserted in the rabies virus genome to replace the G gene. For the rAAV2-retro, the ef1a and CMV promotor was used to drive YFP and Cre-T2A-tagBFP expression, respectively. (c) Structures of AAV helper viruses. The hSyn and ef1a promoter were used to drive TVA, DIO-TVA and DIO-RVG elements