Brain-wide N2cG compensation permits glycoprotein-deleted rabies virus to trace neural circuits across multiple synapses

Rabies-viruses-based retrograde tracers can spread across multiple synapses in a retrograde direction in the nervous system of rodents and primates, making them powerful tools for determining the structure and function of the complicated neural circuits of the brain. However, they have some limitations, such as posing high risks to human health and the inability to retrograde trans-synaptic label inputs from genetically-defined starter neurons. Here, we established a new retrograde trans-multi-synaptic tracing method through brain-wide rabies virus glycoprotein (RVG) compensation, followed by glycoprotein-deleted rabies virus (RV- Δ G) infection in specific brain regions. Furthermore, in combination with the avian tumor virus receptor A (TVA) controlled by a cell-type-specific promoter, we found that EnvA-pseudotyped RV- Δ G can mediate efficient retrograde trans-multi-synaptic transduction from cell-type-specific starter neurons. This study provides new alternative methods for neuroscience researchers to analyze the input neural networks of rodents and nonhuman primates.