Spread of VSV through neurons in the mouse brain.
|To map information transfer in the nervous system, researchers have recently turned to genetically modified viruses capable of infecting specific neurons. When engineered to express a fluorescent protein, these viruses can effectively "trace" neural pathways. Kevin Beier et al. created a viral tracer that can move in selected directions across single or multiple neurons via their connections, or synapses. The researchers modified vesicular stomatitis virus (VSV) to express other viruses' G proteins, membrane proteins that mediate cell-to-cell transmission. In mice, neural tissues injected with VSV expressing G proteins from the rabies virus elicited an infection that progressed across multiple connections from a neuron's termination point, or synapse, to the cell body. A G protein gene from an Arenavirus, which normally infects rodents, allowed the researchers to track neural connections in the opposite direction, from cell body to synapse. Compared with herpes virus strains, which researchers have previously used to map neural connections, VSV is more straightforward to engineer and can infect a greater variety of tissues, the authors report. This VSV tracer will enable researchers to trace single or multiple cells in a circuit that can proceed in either direction, from the cell body to the synapse or from the synapse to the cell body, according to the authors. J.M.|