Imaging brain electric signals with genetically targeted voltage-sensitive fluorescent proteins

Nature Methods

 

7,

 

643–649

 

(2010)

 

doi:10.1038/nmeth.1479

Received

 

23 December 2009

 

Accepted

 

07 June 2010

 

Published online

 

11 July 2010

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Abstract:
Cortical information processing relies on synaptic interactions between diverse classes of neurons with distinct electrophysiological and connection properties. Uncovering the operational principles of these elaborate circuits requires the probing of electrical activity from selected populations of defined neurons. Here we show that genetically encoded voltage-sensitive fluorescent proteins (VSFPs) provide an optical voltage report from targeted neurons in culture, acute brain slices and living mice. By expressing VSFPs in pyramidal cells of mouse somatosensory cortex, we also demonstrate that these probes can report cortical electrical responses to single sensory stimuli in vivo. These protein-based voltage probes will facilitate the analysis of cortical circuits in genetically defined cell populations and are hence a valuable addition to the optogenetic toolbox.

Clarifying brain structure, literally

Nature Methods

 

8,

 

793

 

(2011)

 

doi:10.1038/nmeth.1720

Published online

 

29 September 2011

A fluorescence-compatible tissue-clearing reagent enables light microscopy–based imaging deep in the mouse brain.

In The Invisible Man, a science fiction novella by Herbert G. Wells, the protagonist is a scientist who finds a way to make the human body invisible by changing its refractive index to prevent the bending and reflection of light. In a recent report, Atsushi Miyawaki and his colleagues at RIKEN described the development of a tissue-clearing reagent with similar effects, bridging the gap between science and fiction and enabling fluorescence-based imaging of biological tissues at unprecedented depth and subcellular resolution.

High-resolution microscopy methods and fluorescence-based labeling techniques have enabled the three-dimensional imaging and reconstruction of defined cellular populations in a variety of biological tissues. However, axial resolution and imaging depth are often limited by the intrinsic opacity of biological specimens. For example, in visualizing the mammalian brain, light microscopy–based advances have been confined to the few hundred micrometers under the organ's surface. Alternatively, mechanical sectioning or insertion of minuscule endoscopes can be used to access deeper structures, but such approaches are inevitably laborious, invasive or of limited perspective.

A GFP for RNA

Researchers describe a GFP mimic for fluorescently labeling RNA molecules.

The genetically encodable protein tag GFP and the rainbow of fluorescent variants it inspired have been indispensible for cell biology. Tagging RNAs in cells, however, is not so straightforward.

Samie Jaffrey's lab at Weill Medical College of Cornell University has long been interested in studying the role of RNAs in axon guidance. However, Jaffrey was frustrated that simple tools for visualizing RNAs were not available.

(This article relates to me, as well, because my senior seminar was on axon guidance, and I did not cover RNA mechanisms at all because I did not find any.)