Viral strategies for studying the brain, including a replication‐restricted self‐amplifying delta‐G vesicular stomatis virus that rapidly expresses transgenes in brain and can generate a multicolor golgi‐like expression

Viruses have substantial value as vehicles for transporting transgenes into neurons. Each virus has its own set of attributes for addressing neuroscience‐related questions. Here we review some of the advantages and limitations of herpes, pseudorabies, rabies, adeno‐associated, lentivirus, and others to study the brain. We then explore a novel recombinant vesicular stomatitis virus (dG‐VSV) with the G‐gene deleted and transgenes engineered into the first position of the RNA genome, which replicates only in the first brain cell infected, as corroborated with ultrastructural analysis, eliminating spread of virus. Because of its ability to replicate rapidly and to express multiple mRNA copies and additional templates for more copies, reporter gene expression is amplified substantially, over 500‐fold in 6 hours, allowing detailed imaging of dendrites, dendritic spines, axons, and axon terminal fields within a few hours to a few days after inoculation. Green fluorescent protein (GFP) expression is first detected within 1 hour of inoculation. The virus generates a Golgi‐like appearance in all neurons or glia of regions of the brain tested. Whole‐cell patch‐clamp electrophysiology, calcium digital imaging with fura‐2, and time‐lapse digital imaging showed that neurons appeared physiologically normal after expressing viral transgenes. The virus has a wide range of species applicability, including mouse, rat, hamster, human, and Drosophila cells. By using dG‐VSV, we show efferent projections from the suprachiasmatic nucleus terminating in the periventricular region immediately dorsal to the nucleus. DG‐VSVs with genes coding for different color reporters allow multicolor visualization of neurons wherever applied. J. Comp. Neurol. 516:456–481, 2009. © 2009 Wiley‐Liss, Inc.