| Related Articles |
Targeting Single Neuronal Networks for Gene Expression and Cell Labeling In Vivo.
Neuron. 2010 Aug 26;67(4):562-574
Authors: Marshel JH, Mori T, Nielsen KJ, Callaway EM
To understand fine-scale structure and function of single mammalian neuronal networks, we developed and validated a strategy to genetically target and trace monosynaptic inputs to a single neuron in vitro and in vivo. The strategy independently targets a neuron and its presynaptic network for specific gene expression and fine-scale labeling, using single-cell electroporation of DNA to target infection and monosynaptic retrograde spread of a genetically modifiable rabies virus. The technique is highly reliable, with transsynaptic labeling occurring in every electroporated neuron infected by the virus. Targeting single neocortical neuronal networks in vivo, we found clusters of both spiny and aspiny neurons surrounding the electroporated neuron in each case, in addition to intricately labeled distal cortical and subcortical inputs. This technique, broadly applicable for probing and manipulating single neuronal networks with single-cell resolution in vivo, may help shed new light on fundamental mechanisms underlying circuit development and information processing by neuronal networks throughout the brain.
PMID: 20797534 [PubMed - as supplied by publisher]
This technique of labeling lone neurons by in vivo electroporation and then using the transsynaptic virus system first described earlier by the same lab (Wickersham et al) to label all the presynaptic neurons to that neuron, is potentially really powerful for neuroscience.
That said, I’d think that to claim that they’d “validated” this technique, they would have to show physiological (or other) proof of connectivity. Even one demonstration patched pair would be good. It’s not there. It’s a surprise, too, because in the earlier paper they show a couple of example paired recordings and then specifically say that it will be easier to validate the technique physiologically once it can be limited to single cells. So I’m baffled that the reviewers didn’t ask for this. Maybe there’s some reason it wasn’t feasible in this study?
Agree or Disagree
8 
0
I agree with the comment above. the fact that the authors show no physiology or any other forms of validation to show that the red cells in their images are actually indeed presynaptic partners to the postsynaptic neuron is completely astounding. the first paper from the lab that introduces this technique in cultured slices had some paired recording data to demonstrate positive connections between the presumed pre- and post-synaptic neuron. however, as we well know, the fact that a techniques works well in slice cultures, is in no way a guarantee that it will work in vivo.
Obviously the reviews of this paper was so ‘wowed’ by the fancy virus technique that they didn’t bother to wonder if the results are actually sound. This is too bad, since clearly, if this technique is carefully and properly characterized, even if imperfect (labeling only ~10% of presynaptic neurons), it would be a very powerful tool. But sadly, this paper is far from a quantitative or convincing use of this technique, leaving me wondering…. wtf?!
Agree or Disagree
4 
1
“wowed by the fancy” pretty much describes everything rewarded in science these days. no real desire for insight into function, just pretty techniques.
Agree or Disagree
4 
0
the ~10% of presynaptic neurons calculation presented in this paper is based off of the slice culture technique paper. it’s worth estimating based on those statistics, but actually doing the connectivity assessment in this in vivo setting would have really made this paper strong and pushed the technique as truly labeling connections in vivo.
Agree or Disagree
2 
1