Abstract
Monosynaptic viral tracers are essential tools for dissecting neuronal connectomes and for targeted delivery of molecular sensors and effectors. Viral toxicity and complex multi-injection protocols are major limiting application barriers. To overcome these barriers, we developed an anterograde monosynaptic H129(Amp) tracer system based on HSV-1 strain H129. The H129(Amp) tracer system consists of two components: an H129-dTK-T2-pac(Flox) helper which assists H129(Amp) tracer's propagation and transneuronal monosynaptic transmission. The shared viral features of tracer/helper allow for simultaneous single-injection and subsequent high expression efficiency from multiple-copy of expression cassettes in H129(Amp) tracer. These improvements of H129(Amp) tracer system shorten experiment duration from 28-day to 5-day for fast-bright monosynaptic tracing. The lack of toxic viral genes in the H129(Amp) tracer minimizes toxicity in postsynaptic neurons, thus offering the potential for functional anterograde mapping and long-term tracer delivery of genetic payloads. The H129(Amp) tracer system is a powerful tracing tool for revealing neuronal connectomes.