I've previously discussed some traditional techniques for visualizing specific details in neurons, and this month I'm going to talk about some of the newest fanciest ways to look at cellular scale information.
First off, Array Tomography!
|Micheva et al. 2010 Figure 1 Array Tomography|
Array Tomography combines the enhanced location information of the electron microscopy with the scale and context of immunohistochemistry or in situ hybridization. Not only that, but Array Tomography is done in such a way that the same preparation can be stained for 100s of different proteins. This is a priceless gift to those who want to study protein co-localization. Do certain receptors 'flock together', and if so does a mutation, or drug treatment alter their abundance or proximity to one another?
|Micheva et al. 2010 Figure 4 spine head and neck locations of specific proteins|
And just how do they accomplish this feat?
The trick is in the slicing. Using an ultramicrotome these guys can slice a section of brain 70 nm thin. That's 70 NANOmeters, which is really really thin. (Compare it to 'thick section staining' which works on sections 350,000 nanometers thin). The smallest cellular features, the necks of spines can be as thin as 50-100nm, so 70nm can really capture a lot of detail.
Here is a 'fly through' video of the cortical layers in a cortical column. The red dots are identified synapses, and around 2:11 of the video you get to the pyramidal cell bodies (green) which is pretty stunning.
While "Array Tomography" doesn't quite capture the public imagination like "neurons activated by light", it is huge leap forward in the domain of cellular neuroscience. With array tomography, it becomes possible to investigate co-localization of many proteins in a relatively large section of brain tissue.
Micheva KD, Busse B, Weiler NC, O'Rourke N, & Smith SJ (2010). Single-synapse analysis of a diverse synapse population: proteomic imaging methods and markers. Neuron, 68 (4), 639-53 PMID: 21092855