Transsynaptic viral tools in neural circuit analysis: from anatomical mapping to functional interrogation

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Transsynaptic viral tracers are crucial for mapping neuronal connectivity.
• Current methods include polysynaptic and monosynaptic strategies.

Purpose of the Study:

• To review the advancements and applications of viral tracing techniques in neural circuit analysis.
• To discuss the integration of viral tracing with functional methods.
• To highlight future directions for multisynaptic tracing.

Main Methods:

• Utilized pseudorabies virus (polysynaptic retrograde) and herpes simplex virus (polysynaptic anterograde).
• Employed engineered rabies virus platforms with adeno-associated virus (AAV) helper systems for monosynaptic tracing.
• Integrated viral tracing with functional techniques like calcium imaging and optogenetics.

Main Results:

• Polysynaptic tracers (e.g., pseudorabies virus, HSV) have elucidated multisynaptic organization and output pathways.
• Monosynaptic rabies virus systems enable precise tracing of direct presynaptic partners.
• Integration with functional methods allows for causal interrogation of neuronal populations.

Conclusions:

• Viral tracing has transformed neural circuit analysis from anatomical mapping to functional interrogation.
• Future advancements in polysynaptic tracing, including transgene capacity and functional readouts, are anticipated.
• The field is moving towards more precise and functionally integrated circuit analysis.