Article
All-viral tracing of monosynaptic inputs to single birthdate-defined neurons in the intact brain

https://doi.org/10.1016/j.crmeth.2022.100221Get rights and content
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Highlights

  • Modified rabies virus is used to trace inputs to single cells in deep brain areas

  • Local and distant monosynaptic inputs to single hippocampal cells can be identified

  • Input cells can be functionally characterized in vivo

  • Cells can be targeted based on their birthdate during development

Motivation

Identifying the inputs to a neuron is essential to understand its output. Although this is possible with current methods in many neocortical areas, reaching cells in deeper brain regions in vivo requires removal of tissue that may be part of the circuit under investigation. We developed a virus-based method that enables individual cells in subneocortical areas of wild-type mice to be targeted and their monosynaptic inputs to be identified without removing overlaying tissue.

Summary

Neuronal firing patterns are the result of inputs converging onto single cells. Identifying these inputs, anatomically and functionally, is essential to understand how neurons integrate information. Single-cell electroporation of helper genes and subsequent local injection of recombinant rabies viruses enable precise mapping of inputs to individual cells in superficial layers of the intact cortex. However, access to neurons in deeper structures requires more invasive procedures, including removal of overlying tissue. We developed a method that, through a combination of virus injections, allows us to target 4 or fewer hippocampal cells 48% of the time and a single cell 16% of the time in wild-type mice without use of electroporation or tissue aspiration. We identify local and distant monosynaptic inputs that can be functionally characterized in vivo. By expanding the toolbox for monosynaptic circuit tracing, this method will help further our understanding of neuronal integration at the level of single cells.

Keywords

single cell
monosynaptic tracing
rabies virus
AAV
hippocampus
medial entorhinal cortex
optogenetics
in vivo imaging
calcium imaging

Data and code availability

  • Electrophysiology data used in this manuscript have been deposited online (The DANDI Archive: https://doi.org/10.48324/dandi.000230/0.220506.1516).

  • This paper does not report original code.

  • Any additional information required to reanalyse the data reported in this paper is available from the lead contact upon request.

Cited by (0)

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Present address: Biozentrum, Universität Basel, Basel 4056, Switzerland

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Lead contact