AUTHOR=Lavin Thomas K. , Jin Lei , Lea Nicholas E. , Wickersham Ian R. TITLE=Monosynaptic Tracing Success Depends Critically on Helper Virus Concentrations JOURNAL=Frontiers in Synaptic Neuroscience VOLUME=12 YEAR=2020 URL=https://www.frontiersin.org/journals/synaptic-neuroscience/articles/10.3389/fnsyn.2020.00006 DOI=10.3389/fnsyn.2020.00006 ISSN=1663-3563 ABSTRACT=

Monosynaptically-restricted transsynaptic tracing using deletion-mutant rabies virus (RV) has become a widely used technique in neuroscience, allowing identification, imaging, and manipulation of neurons directly presynaptic to a starting neuronal population. Its most common implementation is to use Cre mouse lines in combination with Cre-dependent “helper” adeno-associated viral vectors (AAVs) to supply the required genes to the targeted population before subsequent injection of a first-generation (ΔG) rabies viral vector. Here we show that the efficiency of transsynaptic spread and the degree of nonspecific labeling in wild-type control animals depend strongly on the concentrations of these helper AAVs. Our results suggest practical guidelines for achieving good results.